op ['äp] -n
- optical art
- operation; operative; operator
- opportunity
- opus
OP -abbr
- observation post
- out of print
opac·i·ty [ō-'pa-sə-tē] -n
- obscurity of sense : unintelligibleness
- the quality or state of being mentally obtuse : dullness
- the quality or state of a body that makes it impervious to the rays of light
- the relative capacity of matter to obstruct the transmission of radiant energy
- an opaque spot in a normally transparent structure (as the lens of the eye)
opah ['ō-pə, -,pä] -n
- a large elliptical laterally compressed marine bony fish ( Lampris guttatusof the family Lampridae) with brilliant colors
opal ['ō-pəl] -n
- a usu. amorphous mineral that is a hydrated silica softer and less dense than quartz and typically with definite and often marked iridescent play of colors and is used esp. as a gem
opal·es·cent [,ō-pə-'le-sᵊnt] -adj, n, adv
- reflecting an iridescent light
opal·ine ['ō-pə-,līn, -,lēn] -adj
- resembling opal
opaque [ō-'pāk] -adj, n, adv
- exhibiting opacity : blocking the passage of radiant energy and esp. light
- hard to understand or explain
- obtuse, thickheaded
opaque projector -n
- a projector using reflected light for projecting an image of an opaque object or matter on an opaque support (as a photograph)
op art ['äp-] -n
- optical art
op cit -abbr
- in the work cited
ope ['ōp] -vb
- open
OPEC -abbr
- Organization of Petroleum Exporting Countries
oped ['äp-'ed] -n
- a page of special features usu. opposite the editorial page of a newspaper
- a feature on such a page
open ['ō-pən, -pᵊm] -adj, adv, n
- having no enclosing or confining barrier : accessible on all or nearly all sides
- cattle grazing on an open range
- being in a position or adjustment to permit passage : not shut or locked
- having a barrier (as a door) so adjusted as to allow passage
- having the lips parted
- stood there with his mouth wide open
- not buttoned or zipped
- completely free from concealment : exposed to general view or knowledge
- their hostilities eventually erupted with open war
- exposed or vulnerable to attack or question : subject
- being an operation or surgical procedure in which an incision is made such that the tissues are fully exposed
- not covered with a top, roof, or lid
- having no protective covering
- : not restricted to a particular group or category of participants: as
- enterable by both amateur and professional contestants
- enterable by a registered voter regardless of political affiliation
- fit to be traveled over : presenting no obstacle to passage or view
- having the parts or surfaces laid out in an expanded position : spread out : unfolded
- low
- formed with the tongue in a lower position
- Italian has an open and a close e
- having clarity and resonance unimpaired by undue tension or constriction of the throat
- produced by an open string or on a wind instrument by the lip without the use of slides, valves, or keys
- available to follow or make use of
- the only course open to us
- not taken up with duties or engagements
- keep an hour open on Friday
- not finally decided : subject to further consideration
- available for a qualified applicant : vacant
- remaining available for use or filling until canceled
- an open order for more items
- available for future purchase
- these items are in open stock
- available for breeding : not now pregnant
- not proprietary : available to third party developers
- : characterized by ready accessibility and usu. generous attitude: as
- generous in giving
- willing to hear and consider or to accept and deal with : responsive
- free from reserve or pretense : frank
- accessible to the influx of new factors (as foreign goods)
- : having openings, interruptions, or spaces: as
- being porous and friable
- sparsely distributed : scattered
- having components separated by a space in writing or printing (as opaque projector)
- not made up of a continuous closed circuit of channels
- the insect circulatory system is open
- not stopped at the top
- not stopped by the finger
- being in operation
- ready for business, patronage, or use
- the store is open from 9 to 5
- the new highway will be open next week
- characterized by lack of effective regulation of various commercial enterprises
- not repressed by legal controls
- free from checking or hampering restraints
- relatively unguarded by opponents
- passed to an open teammate
- having been opened by a first ante, bet, or bid
- characterized by sparing use esp. of the comma
- containing none of its endpoints
- being a set or composed of sets each point of which has a neighborhood all of whose points are contained in the set
- the interior of a sphere is an open set
- being an incomplete electrical circuit
- not allowing the flow of electricity
- having insufficient mass to halt expansion gravitationally
- to move (as a door) from a closed position
- to make available for entry or passage by turning back (as a barrier) or removing (as a cover or an obstruction)
- to make available for or active in a regular function
- to make accessible for a particular purpose
- open ed new land for settlement
- to initiate access to (a computer file) prior to use
- to disclose or expose to view : reveal
- to make more discerning or responsive : enlighten
- must open our minds to the problems
- to bring into view or come in sight of by changing position
- to make an opening in
- to loosen and make less compact
- to spread out : unfold
- to enter upon : begin
- to commence action in a card game by making (a first bid), putting a first bet in (the pot), or playing (a card or suit) as first lead
- to restore or recall (as an order) from a finally determined state to a state in which the parties are free to prosecute or oppose
- to become open
- to spread out : expand
- the wound open ed under the strain
- to become disclosed
- a beautiful vista open ed before us
- to become enlightened or responsive
- to give access
- the rooms open onto a hall
- speak out
- finally he open ed freely on the subject
- to begin a course or activity
- to make a bet, bid, or lead in commencing a round or hand of a card game
- to provide the opening performance of a show before the main event
- opening
- : open and unobstructed space: as
- open air
- open water
- an open contest, competition, or tournament
- a public or unconcealed state or position
open admission -n
- open enrollment
open adoption -n
- an adoption that involves contact between biological and adoptive parents and sometimes between biological parents and the adopted child
openair -adj
- outdoor
open air -n
- the space where air is unconfined
- outdoors
openandshut -adj
- perfectly simple : obvious
- easily settled
- an openandshut case of grand larceny
open arms -n pl
- an eager or warm welcome
- greeted them with open arms
open bar -n
- a bar (as at a wedding reception) at which drinks are served free
open·cast ['ō-pən-,kast] -adj
- worked from a surface open to the air
open chain -n
- an arrangement of atoms represented in a structural formula by a chain whose ends are not joined so as to form a ring
open city -n
- a city that is not occupied or defended by military forces and that is not allowed to be bombed under international law
open dating -n
- the marking of perishable food products with a clearly readable date indicating when the food was packaged or the last date on which it should be sold or used
open door -n, adj
- a recognized right of admittance : freedom of access
- a policy providing such freedom
- a policy giving opportunity for commercial relations with a country to all nations on equal terms
openend -adj
- : organized to allow for contingencies: as
- permitting additional debt to be incurred under the original indenture subject to specified conditions
- having a fluctuating capitalization of shares that are issued or redeemed at the current net asset value or at a figure in fixed ratio to this
- an openend investment company
openend·ed [,ō-pən-'en-dəd] -adj, n
- : not rigorously fixed: as
- adaptable to the developing needs of a situation
- permitting or designed to permit spontaneous and unguided responses
open enrollment -n
- the voluntary enrollment of a student in a public school other than the one assigned on the basis of residence
- enrollment on demand as a student in an institution of higher learning irrespective of formal qualifications
open·er ['ōp-nər, 'ō-pə-] -n
- : one that opens: as
- cards of sufficient value for a player to open the betting in a poker game
- the first item, contest, or event of a series
openeyed [,ō-pən-'īd] -adj
- having the eyes open
- carefully observant : discerning
openfaced [-'fāst] -adj
- served without a covering layer (as of bread or pastry)
open·hand·ed [-'han-dəd] -adj, adv, n
- generous, munificent
openheart -adj
- of, relating to, or performed on a heart temporarily stopped and relieved of circulatory function and surgically opened for repair of defects or damage
open·heart·ed [,ō-pən-'här-təd] -adj, adv, n
- candidly straightforward : frank
- responsive to emotional appeal
openhearth -adj
- of, relating to, involving, or produced in the open-hearth process
openhearth process -n
- a process of making steel from pig iron in a reverberatory furnace equipped with a regenerator
open house -n
- ready and usu. informal hospitality or entertainment for all comers
- a house or apartment open for inspection esp. by prospective buyers or tenants
open·ing ['ōp-niŋ, 'ō-pə-] -n
- an act or instance of making or becoming open
- an act or instance of beginning : commencement
- a formal and usu. public event by which something new is put officially into operation
- : something that is open: as
- breach, aperture
- an open width : span
- an area without trees or with scattered usu. mature trees that occurs as a break in a forest
- two pages that face one another in a book
- : something that constitutes a beginning: as
- a usu. planned series of moves made at the beginning of a game of chess or checkers
- a first performance
- occasion, chance
- an opportunity for employment
openlabel -adj
- being or relating to a clinical trial in which the treatment given to each subject is not concealed from either the experimenters or the subject
- an openlabel multicenter study
open letter -n
- a published letter of protest or appeal usu. addressed to an individual but intended for the general public
open loop -n
- a control system for an operation or process in which there is no self-correcting action as there is in a closed loop
open marriage -n
- a marriage in which the partners agree to let each other have sexual partners outside the marriage
open mike -n
- an event in which amateurs may perform (as at a coffeehouse) usu. without auditioning first
openmind·ed [,ō-pən-'mīn-dəd] -adj, adv, n
- receptive to arguments or ideas
open·mouthed [,ō-pən-'mau̇thd, -'mau̇tht] -adj, adv, n
- clamorous, vociferous
- having the mouth wide open
- struck with amazement or wonder
openpol·li·nat·ed [,ō-pən-'pä-lə-,nā-təd] -adj
- pollinated by natural agencies (as wind or insects) without human intervention
open season -n
- a period when it is legal to kill or catch game or fish protected at other times by law
- a time during which someone or something is the object of sustained attack or criticism
open secret -n
- a supposedly secret but generally known matter
open sentence -n
- a statement (as in mathematics) that contains at least one blank or unknown and that becomes true or false when the blank is filled or a quantity is substituted for the unknown
open ses·a·me [-'se-sə-mē] -n
- something that unfailingly brings about a desired end
open shop -n
- an establishment in which eligibility for employment and retention on the payroll are not determined by membership or nonmembership in a labor union though there may be an agreement by which a union is recognized as sole bargaining agent
open sight -n
- a firearm rear sight having an open notch
open stance -n
- a stance (as in golf) in which the forward foot is farther from the line of play than the back foot
open syllable -n
- a syllable ended by a vowel or diphthong
open up -vt
- to make available
- to make plain or visible : disclose
- to open by cutting into
- to spread out or come into view
- to commence firing
- to become communicative
- tried to get the patient to open up
open·work ['ō-pən-,wərk] -n, adj
- work constructed so as to show openings through its substance : work that is perforated or pierced
opera ['ō-pəs] -n
(variant of opus)
- work
- a musical composition or set of compositions usu. numbered in the order of its issue
op·era ['ä-p(ə-)rə, Southern also 'ä-prē] -n
- a drama set to music and made up of vocal pieces with orchestral accompaniment and orchestral overtures and interludes
- grand opera
- the score of a musical drama
- the performance of an opera
- a house where operas are performed
op·er·a·ble ['ä-p(ə-)rə-bəl] -adj, n, adv
- fit, possible, or desirable to use : practicable
- likely to result in a favorable outcome upon surgical treatment
op·era bouffe ['ō-pā-rä-'büf, 'ä-p(ə-)rə-] -n
- satirical comic opera
opera buf·fa [-'bü-fə] -n
- an 18th century farcical comic opera with dialogue in recitative
opera co·mique [-kä-'mēk, -kō-] -n
- an opera characterized by spoken dialogue interspersed between the arias and ensemble numbers
opera glass -n
- a small low-power binocular without prisms for use at the opera or theater often used in pl.
op·era·go·er ['ä-p(ə-)rə-,gō-ər] -n
- a person who frequently goes to operas
opera hat -n
- a man's collapsible top hat
opera house -n
- a theater devoted principally to the performance of operas
- theater
op·er·and [,ä-pə-'rand] -n
- something (as a quantity or data) that is operated on (as in a mathematical operation)
- the address in a computer instruction of data to be operated on
op·er·ant ['ä-pə-rənt] -adj, adv
- functioning or tending to produce effects : effective
- of or relating to the observable or measurable
- of, relating to, or being an operant or operant conditioning
operant -n
- behavior (as bar pressing by a rat to obtain food) that operates on the environment to produce rewarding and reinforcing effects
operant conditioning -n
- conditioning in which the desired behavior or increasingly closer approximations to it are followed by a rewarding or reinforcing stimulus
opera se·ria [-'ser-ē-ə, -'sir-] -n
- an 18th century opera with a heroic or legendary subject
op·er·ate ['ä-pə-,rāt, 'ä-,prāt] -vb
- to perform a function : exert power or influence
- factors operating against our success
- to produce an appropriate effect
- the drug operated quickly
- to perform an operation or a series of operations
- to perform surgery
- to carry on a military or naval action or mission
- to follow a course of conduct that is often irregular
- crooked gamblers operating in the club
- bring about, effect
- to cause to function : work
- to put or keep in operation
- to perform an operation on
- to perform surgery on
op·er·at·ic [,ä-pə-'ra-tik] -adj, adv
- of or relating to opera
- grand, dramatic, or romantic in style or effect
operating -adj
- of, relating to, or used for or in operations
- a hospital operating room
operating system -n
- software that controls the operation of a computer and directs the processing of programs (as by assigning storage space in memory and controlling input and output functions)
op·er·a·tion [,ä-pə-'rā-shən] -n
- performance of a practical work or of something involving the practical application of principles or processes
- an exertion of power or influence
- the quality or state of being functional or operative
- the plant is now in operation
- a method or manner of functioning
- a machine of very simple operation
- efficacy, potency archaic except in legal usage
- a procedure performed on a living body usu. with instruments esp. for the repair of damage or the restoration of health
- any of various mathematical or logical processes (as addition) of deriving one entity from others according to a rule
- a usu. military action, mission, or maneuver including its planning and execution
- the office on the flight line of an airfield where pilots file clearance for flights and where flying from the field is controlled
- the agency of an organization charged with carrying on the principal planning and operating functions of a headquarters and its subordinate units
- a business transaction esp. when speculative
- a single step performed by a computer in the execution of a program
- a usu. small business or establishment
- ran a struggling operation
op·er·a·tion·al [-shnəl, -shə-nᵊl] -adj, adv
- of or relating to operation or to an operation
- the operational gap between planning and production
- of, relating to, or based on operations
- of, engaged in, or connected with execution of military or naval operations in campaign or battle
- ready for or in condition to undertake a destined function
op·er·a·tion·al·ism [-shnə-,li-zəm, -shə-nə-,li-zəm] -n, adj
- a view that the concepts or terms used in nonanalytic scientific statements must be definable in terms of identifiable and repeatable operations
op·er·a·tion·ism [,ä-pə-'rā-shə-,ni-zəm] -n
- operationalism
operations research -n
- the application of scientific and esp. mathematical methods to the study and analysis of problems involving complex systems called also operational research
op·er·a·tive ['ä-p(ə-)rə-tiv, 'ä-pə-,rā-] -adj, adv, n
- producing an appropriate effect : efficacious
- most significant or essential
- the operative word in a phrase
- exerting force or influence : operating
- having to do with physical operations (as of machines)
- working
- based on or consisting of an operation
operative -n
- : operator: as
- artisan, mechanic
- a secret agent
- private detective
- a person who works toward achieving the objectives of a larger interest
op·er·a·tor ['ä-pə-,rā-tər, 'ä-,prā-] -n, adj
- : one that operates: as
- one that operates a machine or device
- one that operates a business
- one that performs surgical operations
- one that deals in stocks or commodities
- mountebank, fraud
- a shrewd and skillful person who knows how to circumvent restrictions or difficulties
- something and esp. a symbol that denotes or performs a mathematical or logical operation
- a mathematical function
- a binding site in a DNA chain at which a genetic repressor binds to inhibit the initiation of transcription of messenger RNA by one or more nearby structural genes called also operator gene
oper·cu·lar [ō-'pər-kyə-lər] -adj
- of, relating to, or constituting an operculum
opercular -n
- an opercular part (as a bone or scale)
oper·cu·late [ō-'pər-kyə-lət] -adj
- having an operculum
oper·cu·lum [ō-'pər-kyə-ləm] -n
- : a body process or part that suggests a lid: as
- a horny or shelly plate on the posterior dorsal surface of the foot in many gastropod mollusks that closes the shell when the animal is retracted
- the covering of the gills of a fish
- a lid or covering flap (as of a moss capsule)
op·er·et·ta [,ä-pə-'re-tə] -n
- a usu. romantic comic opera that includes songs and dancing
op·er·on ['ä-pə-,rän] -n
- a group of closely linked genes that produces a single messenger RNA molecule in transcription and that consists of structural genes and regulating elements (as an operator and promoter)
op·er·ose ['ä-pə-,rōs] -adj, adv, n
- tedious, wearisome
Ophe·lia [ō-'fēl-yə] -n
- the daughter of Polonius in Shakespeare's Hamlet
ophid·i·an [ō-'fi-dē-ən] -adj, n
- of, relating to, or resembling snakes
Ophir ['ō-fər] -n
- a biblical land of uncertain location but reputedly rich in gold
ophit·ic [ä-'fi-tik, ō-] -adj
- having or being a rock fabric in which lath-shaped plagioclase crystals are enclosed in later formed augite
ophi·u·roid [,ō-fē-'yu̇r-,ȯid, ,ä-] -n, adj
- brittle star
ophthalm- -comb form
- eye
oph·thal·mia [äf-'thal-mē-ə, äp-] -n
- inflammation of the conjunctiva or the eyeball
oph·thal·mic [-mik] -adj
- of, relating to, or situated near the eye
- supplying or draining the eye or structures in the region of the eye
oph·thal·mol·o·gist [,äf-thə(l)-'mä-lə-jist, ,äp-, -,thal-] -n
- a physician who specializes in ophthalmology
oph·thal·mol·o·gy [-'mä-lə-jē] -n, adj, adv
- a branch of medical science dealing with the structure, functions, and diseases of the eye
oph·thal·mo·scope [äf-'thal-mə-,skōp, äp-] -n, adj
- an instrument for use in viewing the interior of the eye and esp. the retina
opi·ate ['ō-pē-ət, -,āt] -n
- a drug (as morphine or codeine) containing or derived from opium and tending to induce sleep and alleviate pain
- narcotic
- opioid
- something that induces rest or inaction or quiets uneasiness
opiate -adj
- containing or mixed with opium
- of, relating to, binding, or being an opiate
- inducing sleep : narcotic
- causing dullness or inaction
opine [ō-'pīn] -vb
- to express opinions
- to state as an opinion
opin·ion [ə-'pin-yən] -n, adj
- a view, judgment, or appraisal formed in the mind about a particular matter
- approval, esteem
- belief stronger than impression and less strong than positive knowledge
- a generally held view
- a formal expression of judgment or advice by an expert
- the formal expression (as by a judge, court, or referee) of the legal reasons and principles upon which a legal decision is based
opin·ion·at·ed [-yə-,nā-təd] -adj, adv, n
- unduly adhering to one's own opinion or to preconceived notions
opin·ion·a·tive [-,nā-tiv] -adj, adv, n
- of, relating to, or consisting of opinion : doctrinal
- opinionated
opi·oid ['ō-pē-,ȯid] -adj
- possessing some properties characteristic of opiate narcotics but not derived from opium
- of, involving, or induced by an opioid
opioid -n
- any of a group of endogenous neural polypeptides (as an endorphin or enkephalin) that bind esp. to opiate receptors and mimic some of the pharmacological properties of opiates called also opioid peptide
- a synthetic drug possessing narcotic properties similar to opiates but not derived from opium
- opiate
opis·tho·branch [ə-'pis-thə-,braŋk] -n, adj
- any of a subclass (Opisthobranchia) of marine gastropod mollusks that have the gills when present posterior to the heart and often lack a shell
opi·um ['ō-pē-əm] -n
- a bitter brownish addictive narcotic drug that consists of the dried latex obtained from immature seed capsules of the opium poppy
- something having an effect like that of opium
opium poppy -n
- an annual Eurasian poppy ( Papaver somniferum) cultivated since antiquity as the source of opium, for its edible oily seeds, or for its showy flowers
opos·sum [(ə-)'pä-səm] -n
- any of a family (Didelphidae) of American marsupials that usu. have a pointed snout and prehensile tail
- a common omnivorous largely nocturnal mammal ( Didelphis virginiana) of No. America that has grayish to blackish fur with white on the cheeks and is an expert climber
- any of several Australian phalangers
opp -abbr
- opposite
op·po·nent [ə-'pō-nənt] -n
- one that takes an opposite position (as in a debate, contest, or conflict)
- a muscle that opposes or counteracts and limits the action of another
opponent -adj
- antagonistic, opposing
- situated in front
op·por·tune [,ä-pər-'tün, -'tyün] -adj, adv, n
- suitable or convenient for a particular occurrence
- occurring at an appropriate time
- an opportune offer of assistance
op·por·tun·ism [-'tü-,ni-zəm, -'tyü-] -n
- the art, policy, or practice of taking advantage of opportunities or circumstances often with little regard for principles or consequences
op·por·tun·ist [-'tü-nist, -'tyü-] -n, adj
- one that is opportunistic or that practices opportunism
op·por·tu·nis·tic [-tü-'nis-tik, -tyü-] -adj, adv
- : taking advantage of opportunities as they arise: as
- exploiting opportunities with little regard to principle or consequences
- a politician considered opportunistic
- feeding on whatever food is available
- being or caused by a usu. harmless microorganism that can become pathogenic when the host's resistance is impaired
op·por·tu·ni·ty [,ä-pər-'tü-nə-tē, -'tyü-] -n
- a favorable juncture of circumstances
- the halt provided an opportunity for rest and refreshment
- a good chance for advancement or progress
opportunity cost -n
- the added cost of using resources (as for production or speculative investment) that is the difference between the actual value resulting from such use and that of an alternative (as another use of the same resources or an investment of equal risk but greater return)
op·pos·able [ə-'pō-zə-bəl] -adj, n
- capable of being opposed or resisted
- capable of being placed against one or more of the remaining digits of a hand or foot
- the opposable human thumb
op·pose [ə-'pōz] -vt, n
- to place over against something so as to provide resistance, counterbalance, or contrast
- to place opposite or against something
- to offer resistance to
op·posed [-'pōzd] -adj
- set or placed in opposition : contrary
- with politicians, as opposed to soap, you cannot return what you have bought -- Felix G. Rohatyn
op·pose·less [ə-'pōz-ləs] -adj
- irresistible
op·po·site ['ä-pə-zət, 'äp-sət] -adj, adv, n
- set over against something that is at the other end or side of an intervening line or space
- opposite ends of a diameter
- situated in pairs on an axis with each member being separated from the other by half the circumference of the axis
- occupying an opposing and often antagonistic position
- opposite sides of the question
- diametrically different (as in nature or character)
- contrary to one another or to a thing specified : reverse
- gave them opposite directions
- being the other of a pair that are corresponding or complementary in position, function, or nature
- members of the opposite sex
- of, relating to, or being the side of a baseball field that is near the first base line for a right-handed batter and near the third base line for a left-handed batter
opposite -n
- something that is opposed to some other often specified thing
- antonym
- additive inverse
- the additive inverse of a real number
- on or to an opposite side
- across from and usu. facing or on the same level with
- in a role complementary to
- played opposite the leading man in the comedy
opposite number -n
- a member of a system or class who holds relatively the same position as a particular member in a corresponding system or class : counterpart
op·po·si·tion [,ä-pə-'zi-shən] -n, adj
- a configuration in which one celestial body is opposite another (as the sun) in the sky or in which the elongation is near or equal to 180 degrees
- the relation between two propositions having the same subject and predicate but differing in quantity or quality or both
- an act of setting opposite or over against : the condition of being so set
- hostile or contrary action or condition
- something that opposes
- a body of persons opposing something
- a political party opposing and prepared to replace the party in power
op·po·si·tion·ist [-'zi-sh(ə-)nist] -n, adj
- a member of an opposition
op·press [ə-'pres] -vt, n
- suppress
- to crush or burden by abuse of power or authority
- to burden spiritually or mentally : weigh heavily upon
op·pres·sion [ə-'pre-shən] -n
- unjust or cruel exercise of authority or power
- something that oppresses esp. in being an unjust or excessive exercise of power
- a sense of being weighed down in body or mind : depression
op·pres·sive [ə-'pre-siv] -adj, adv, n
- unreasonably burdensome or severe
- tyrannical
- overwhelming or depressing to the spirit or senses
op·pro·bri·ous [ə-'prō-brē-əs] -adj, adv, n
- expressive of opprobrium : scurrilous
- deserving of opprobrium : infamous
op·pro·bri·um [-brē-əm] -n
- something that brings disgrace
- public disgrace or ill fame that follows from conduct considered grossly wrong or vicious
- contempt, reproach
op·pugn [ə-'pyün, ä-] -vt, n
- to fight against
- to call in question
Ops ['äps] -n
- the Roman goddess of abundance and the wife of Saturn
op·sin ['äp-sən] -n
- any of various colorless proteins that in combination with retinal or a related prosthetic group form a visual pigment (as rhodopsin) in a reaction reversible by light
op·son·ic [äp-'sä-nik] -adj
- of, relating to, or involving opsonin
op·so·nin ['äp-sə-nən] -n
- any of various proteins (as antibodies or complement) that bind to foreign particles and cells (as bacteria) making them more susceptible to the action of phagocytes
opt ['äpt] -vi
- to make a choice
- to decide in favor of something
- opt ed for a tax increase -- Tom Wicker
- optical; optician; optics
- option; optional
op·ta·tive ['äp-tə-tiv] -adj, n, adv
- of, relating to, or constituting a verbal mood that is expressive of wish or desire
- of, relating to, or constituting a sentence that is expressive of wish or hope
- expressing desire or wish
op·tic ['äp-tik] -adj
- of or relating to vision or the eye
optic -n
- eye
- any of the elements (as lenses, mirrors, or light guides) of an optical instrument or system usu. used in pl.
- an optical instrument
op·ti·cal ['äp-ti-kəl] -adj, adv
- of or relating to the science of optics
- of or relating to vision : visual
- visible
- of, relating to, or being objects that emit light in the visible range of frequencies
- using the properties of light to aid vision
- of, relating to, or utilizing light esp. instead of other forms of energy
- involving the use of light-sensitive devices to acquire information for a computer
- optical character recognition
- of or relating to optical art
optical activity -n
- ability of a chemical substance to rotate the plane of vibration of polarized light to the right or left
optical art -n
- nonobjective art characterized by the use of straight or curved lines or geometric patterns often for an illusory effect (as of motion)
optical bench -n
- an apparatus that is fitted for the convenient location and adjustment of light sources and optical devices and that is used for the observation and measurement of optical phenomena
optical disk -n
- a disk with a plastic coating on which information (as music, visual images, or computer data) is recorded digitally (as in the form of tiny pits) and which is read by using a laser
optical fiber -n
- a single fiber-optic strand
optical glass -n
- flint or crown glass of well-defined characteristics used esp. for making lenses
optical illusion -n
- illusion
optically active -adj
- capable of rotating the plane of vibration of polarized light to the right or left used of compounds, molecules, or atoms
optical rotation -n
- the angle through which the plane of vibration of polarized light that traverses an optically active substance is rotated
optic axis -n
- a line in a doubly refracting medium that is parallel to the direction in which all components of plane-polarized light travel with the same speed
optic chiasma -n
- the X-shaped partial decussation on the undersurface of the hypothalamus through which the optic nerves are continuous with the brain called also optic chiasm
optic cup -n
- the optic vesicle after invaginating to form a 2-layered cup from which the retina and pigmented layer of the eye will develop called also eyecup
optic disk -n
- blind spot
op·ti·cian [äp-'ti-shən] -n
- a maker of or dealer in optical items and instruments
- a person who reads prescriptions for visual correction, orders lenses, and dispenses eyeglasses and contact lenses
optic lobe -n
- either of two prominences of the midbrain concerned with vision
optic nerve -n
- either of the second pair of cranial nerves that pass from the retina to the optic chiasma and conduct visual stimuli to the brain
op·tics ['äp-tiks] -n pl but sing in constr
- a science that deals with the genesis and propagation of light, the changes that it undergoes and produces, and other phenomena closely associated with it
optic vesicle -n
- an evagination of each lateral wall of the embryonic vertebrate forebrain from which the nervous structures of the eye develop
op·ti·mal ['äp-tə-məl] -adj, n, adv
- most desirable or satisfactory : optimum
op·ti·mi·sa·tion [,äp-tə-mə-'zā-shən] -n
(variant of optimization)
- an act, process, or methodology of making something (as a design, system, or decision) as fully perfect, functional, or effective as possible
- the mathematical procedures (as finding the maximum of a function) involved in this
op·ti·mism ['äp-tə-,mi-zəm] -n, adj, adv
- a doctrine that this world is the best possible world
- an inclination to put the most favorable construction upon actions and events or to anticipate the best possible outcome
Op·ti·mist ['äp-tə-mist] -n
- a member of a major international service club
op·ti·mi·za·tion [,äp-tə-mə-'zā-shən] -n
- an act, process, or methodology of making something (as a design, system, or decision) as fully perfect, functional, or effective as possible
- the mathematical procedures (as finding the maximum of a function) involved in this
op·ti·mize ['äp-tə-,mīz] -vt, n
- to make as perfect, effective, or functional as possible
op·ti·mum ['äp-tə-məm] -n, adj
- the amount or degree of something that is most favorable to some end
- the most favorable condition for the growth and reproduction of an organism
- greatest degree attained or attainable under implied or specified conditions
op·tion ['äp-shən] -n
- an act of choosing
- the power or right to choose : freedom of choice
- a privilege of demanding fulfillment of a contract on any day within a specified time
- a contract conveying a right to buy or sell designated securities, commodities, or property interest at a specified price during a stipulated period
- the right conveyed by an option
- a right of an insured person to choose the form in which payments due on a policy shall be made or applied
- : something that may be chosen: as
- an alternative course of action
- didn't have many option s open
- an item that is offered in addition to or in place of standard equipment
- an offensive football play in which a back may choose whether to pass or run with the ball called also option play
option -vt
- to grant or take an option on
- to acquire the exclusive right to use (an author's work) as the basis for a motion picture
- the studio option ed the novel for a film
op·tion·al ['äp-shnəl, -shə-nᵊl] -adj, n, adv
- involving an option : not compulsory
opto- -comb form
- vision
- optic and
op·to·elec·tron·ics [,äp-(,)tō-i-lek-'trä-niks, -ē-lek-] -n pl but sing in constr, adj
- a branch of electronics that deals with electronic devices for emitting, modulating, transmitting, and sensing light
op·to·ki·net·ic [,äp-tō-kə-'ne-tik, -kī-] -adj
- of, relating to, or involving movements of the eyes
op·tom·e·trist [äp-'tä-mə-trist] -n
- a specialist licensed to practice optometry
op·tom·e·try [-trē] -n, adj
- the health-care profession concerned esp. with examining the eye for defects and faults of refraction, with prescribing correctional lenses or eye exercises, with diagnosing diseases of the eye, and with treating such diseases or referring them for treatment
opt out -vi
- to choose not to participate in something often used with of
op·u·lence ['ä-pyə-lən(t)s] -n
- wealth, affluence
- abundance, profusion
op·u·lent [-lənt] -adj, adv
- : exhibiting or characterized by opulence: as
- having a large estate or property : wealthy
- hoping to marry an opulent widow
- amply or plentifully provided or fashioned often to the point of ostentation
- living in opulent comfort
opun·tia [ō-'pən(t)-sh(ē-)ə] -n
- any of a large genus ( Opuntia) of American cacti with usu. yellow flowers and flat or terete joints usu. studded with tubercles bearing spines or prickly hairs
opus ['ō-pəs] -n
- work
- a musical composition or set of compositions usu. numbered in the order of its issue
opus·cule [ō-'pəs-(,)kyül] -n
- a small or petty work : opusculum
opus·cu·lum [ō-'pəs-kyə-ləm] -n
- a minor work (as of literature) usu. used in pl.