ur- -comb form

  1. urine
    • ur ic
  2. urinary tract
    • uro logy
  3. urinary and
    • uro genital
  4. urea
    • ur acil
  5. tail
    • uro pod
  6. original : primitive
    • ur- form
  7. original version of
    • ur text
  8. prototypical : arch-
    • ur- anticommunist

ura·cil ['yu̇r-ə-,sil, -səl] -n

  1. a pyrimidine base C 4H 4N 2O 2that is one of the four bases coding genetic information in the polynucleotide chain of RNA

urae·us [yu̇-'rē-əs] -n

  1. a representation of the sacred asp ( Naja haje) appearing in ancient Egyptian art and esp. on the headdress of rulers and serving as a symbol of sovereignty

UralAl·ta·ic [,yu̇r-əl-al-'tā-ik] -n, adj

  1. a postulated language family comprising the Uralic and Altaic languages

Ura·li·an [yu̇-'rā-lē-ən, -'ra-] -adj

  1. of or relating to the Ural mountains
  2. uralic

Ural·ic [yu̇-'ra-lik] -n

  1. a language family comprising the Finno-Ugric and Samoyed languages

Uralic -adj

  1. of, relating to, or constituting the Finno-Ugric and Samoyed languages

Ura·nia [yu̇-'rā-nē-ə, -nyə] -n

  1. the Greek Muse of astronomy

Ura·ni·an [yu̇-'rā-nē-ən, -nyən] -adj

  1. of or relating to the planet Uranus

ura·ni·nite [yu̇-'rā-nə-,nīt] -n

  1. a black octahedral mineral that consists of an oxide of uranium which usu. contains thorium, lead, and rare earth elements and is the chief ore of uranium

ura·ni·um [yu̇-'rā-nē-əm] -n

  1. a silvery heavy radioactive polyvalent metallic element that is found esp. in uraninite and exists naturally as a mixture of mostly nonfissionable isotopes

uranium hexa·flu·o·ride [-,hek-sə-'flȯr-,īd, -'flu̇r-] -n

  1. a volatile compound UF 6of uranium and fluorine that is used in one major process of enriching uranium in uranium 235

uranium 238 -n

  1. an isotope of uranium of mass number 238 that is the most stable uranium isotope, that constitutes over 99 percent of natural uranium, that is not fissile but can be used to produce a fissile isotope of plutonium, and that has a half-life of 4.5 billion years

uranium 235 -n

  1. a light isotope of uranium of mass number 235 that constitutes less than one percent of natural uranium, that when bombarded with slow neutrons undergoes rapid fission into smaller atoms with the release of neutrons and energy, and that is used in nuclear reactors and atomic bombs

ura·nog·ra·phy [,yu̇r-ə-'nä-grə-fē] -n

  1. the construction of celestial representations (as maps)

Ura·nus ['yu̇r-ə-nəs, yu̇-'rā-] -n

  1. the sky personified as a god and father of the Titans in Greek mythology
  2. the planet seventh in order from the sun

ura·nyl ['yu̇r-ə-,nil, yu̇-'rā-nᵊl] -n

  1. a divalent radical UO 2

urate ['yu̇r-,āt] -n, adj

  1. a salt of uric acid

ur·ban ['ər-bən] -adj

  1. of, relating to, characteristic of, or constituting a city

ur·bane [,ər-'bān] -adj, adv

  1. notably polite or polished in manner

ur·ban·i·sa·tion [,ər-bə-nə-'zā-shən] -n

(variant of urbanization)

  1. the quality or state of being urbanized or the process of becoming urbanized

ur·ban·ism ['ər-bə-,ni-zəm] -n

  1. the characteristic way of life of city dwellers
  2. the study of the physical needs of urban societies
  3. city planning
  4. urbanization

ur·ban·ist ['ər-bə-nist] -n, adj, adv

  1. a specialist in city planning

ur·ban·ite ['ər-bə-,nīt] -n

  1. a person who lives in a city

ur·ban·i·ty [,ər-'ba-nə-tē] -n

  1. the quality or state of being urbane
  2. urbane acts or conduct

ur·ban·i·za·tion [,ər-bə-nə-'zā-shən] -n

  1. the quality or state of being urbanized or the process of becoming urbanized

ur·ban·ize ['ər-bə-,nīz] -vt

  1. to cause to take on urban characteristics
    • urbanized areas
  2. to impart an urban way of life to
    • urbanize migrants from rural areas

urban legend -n

  1. an often lurid story or anecdote that is based on hearsay and widely circulated as true
    • the urban legend of alligators living in the sewers
    called also urban myth

ur·ban·ol·o·gy [,ər-bə-'nä-lə-jē] -n

  1. a study dealing with specialized problems of cities (as planning, education, sociology, and politics)

urban renewal -n

  1. a construction program to replace or restore substandard buildings in an urban area

urban sprawl -n

  1. the spreading of urban developments (as houses and shopping centers) on undeveloped land near a city

ur·ce·o·late [,ər-'sē-ə-lət, 'ər-sē-ə-,lāt] -adj

  1. shaped like an urn
    • urceolate corollas

ur·chin ['ər-chən] -n

  1. hedgehog
  2. a mischievous and often poor and raggedly clothed youngster
    • street urchin s
  3. sea urchin

urd ['u̇rd, 'ərd] -n

  1. an annual Asian legume ( Vigna mungosyn. Phaseolus mungo) widely grown in warm regions for its edible blackish seed, for green manure, or for forage
  2. the seed

Ur·du ['u̇r-(,)dü, 'ər-] -n

  1. an Indo-Aryan language that has the same colloquial basis as standard Hindi, is an official language of Pakistan, and is widely used by Muslims in urban areas of India

urea [yu̇-'rē-ə] -n

  1. a soluble weakly basic nitrogenous compound CO(NH 2) 2that is the chief solid component of mammalian urine and an end product of protein decomposition, is synthesized from carbon dioxide and ammonia, and is used esp. in synthesis (as of resins and plastics) and in fertilizers and animal rations

ureaformaldehyde -n

  1. a thermosetting synthetic resin made by condensing urea with formaldehyde

ure·ase ['yu̇r-ē-,ās, -,āz] -n

  1. an enzyme that catalyzes the hydrolysis of urea

ure·din·i·um [,yu̇r-ə-'di-nē-əm] -n, adj

  1. a usu. reddish or black mass of hyphae and spores of a rust fungus forming pustules that rupture the host's cuticle

ure·do·spore [yu̇-'rē-də-,spȯr] -n

  1. one of the thin-walled spores that are produced by uredinial hyphae and spread the fungus vegetatively

ure·ide ['yu̇r-ē-,īd] -n

  1. a cyclic or acyclic acyl derivative of urea

ure·mia [yu̇-'rē-mē-ə] -n, adj

  1. accumulation in the blood of constituents normally eliminated in the urine that produces a severe toxic condition and usu. occurs in severe kidney disease
  2. the toxic bodily condition associated with uremia

ureo·tel·ic [yu̇-,rē-ə-'te-lik, ,yu̇r-ē-ō-] -adj, n

  1. excreting nitrogen mostly in the form of urea

ure·ter ['yu̇r-ə-tər, yu̇-'rē-tər] -n, adj

  1. a duct that carries away the urine from a kidney to the bladder or cloaca

ure·thane ['yu̇r-ə-,thān] -n

  1. a crystalline compound C 3H 7NO 2that is the ethyl ester of carbamic acid and is used esp. as a solvent and medicinally as an antineoplastic agent
  2. an ester of carbamic acid other than the ethyl ester
  3. polyurethane

ure·thra [yu̇-'rē-thrə] -n, adj

  1. the canal that in most mammals carries off the urine from the bladder and in the male serves also as a passageway for semen

ure·thri·tis [,yu̇r-i-'thrī-təs] -n

  1. inflammation of the urethra

ure·thro·scope [yu̇-'rē-thrə-,skōp] -n

  1. an instrument for viewing the interior of the urethra

urge ['ərj] -vb, n

  1. to present, advocate, or demand earnestly or pressingly
    • his conviction was upheld on a theory never urged at his...trial -- Leon Friedman
  2. to undertake the accomplishment of with energy, swiftness, or enthusiasm
    • urge the attack
  3. solicit, entreat
    • urged him to keep trying
  4. to serve as a motive or reason for
    • urged by a sense of duty
  5. to force or impel in an indicated direction or into motion or greater speed
    • the dog urged the sheep toward the gate
  6. stimulate, provoke
    • urge not my father's anger -- Shak.
  7. to declare, advance, or press earnestly a statement, argument, charge, or claim
    • urged for the adoption of the proposal
  8. the act or process of urging
  9. a force or impulse that urges
  10. a continuing impulse toward an activity or goal

urge incontinence -n

  1. involuntary leakage of urine from the bladder when a sudden strong need to urinate is felt

ur·gen·cy ['ər-jən(t)-sē] -n

  1. the quality or state of being urgent : insistence
  2. a force or impulse that impels or constrains : urge

ur·gent ['ər-jənt] -adj, adv

  1. calling for immediate attention : pressing
    • urgent appeals
    • an urgent need
  2. conveying a sense of urgency
  3. urging insistently : importunate

uri·al ['u̇r-ē-əl, -,äl] -n

  1. an upland wild sheep ( Ovis vignei) of southern and central Asia which is reddish brown and the males of which have a beard from the neck to the chest

uric ['yu̇r-ik] -adj

  1. of, relating to, or found in urine

uric acid -n

  1. a white odorless and tasteless nearly insoluble acid C 5H 4N 4O 3that is the chief nitrogenous waste present in the urine esp. of lower vertebrates (as birds and reptiles), is present in small quantity in human urine, and occurs pathologically in renal calculi and the tophi of gout

uri·co·su·ric [,yu̇r-i-kə-'shu̇r-ik, -'su̇r-] -adj

  1. relating to or promoting the excretion of uric acid in the urine

uri·co·tel·ic [,yu̇r-i-kō-'te-lik] -adj, n

  1. excreting nitrogen mostly in the form of uric acid
    • birds are typical uricotelic animals

uri·dine ['yu̇r-ə-,dēn] -n

  1. a ribonucleoside C 9H 12N 2O 6containing uracil that in the form of phosphate derivatives plays an important role in carbohydrate metabolism

Uri·el ['yu̇r-ē-əl] -n

  1. one of the four archangels named in Hebrew tradition

Urim and Thum·mim [,yu̇r-ə-mən(d)-'thə-məm, ,u̇r-; ,u̇r-ēm-ən(d)-'tu̇-mēm] -n pl

  1. sacred lots used in early times by the Hebrews

urin- -comb form

  1. ur-
    • urino genital
    • urin ary

uri·nal ['yər-ə-nᵊl, 'yu̇r-, Brit also yu̇-'rī-nᵊl] -n

  1. a vessel for receiving urine
  2. a building or enclosure with facilities for urinating
  3. a fixture used for urinating

uri·nal·y·sis [,yər-ə-'na-lə-səs, ,yu̇r-] -n

  1. chemical analysis of urine

uri·nary ['yər-ə-,ner-ē, 'yu̇r-] -adj

  1. relating to, occurring in, affecting, or constituting the organs concerned with the formation and discharge of urine
    • the urinary system
    • the urinary tract
    • urinary calculi
  2. of, relating to, or for urine
  3. excreted as or in urine
    • urinary sugar

urinary bladder -n

  1. a membranous sac in many vertebrates that serves for the temporary retention of urine and discharges by the urethra

uri·nate ['yər-ə-,nāt, 'yu̇r-] -vi, n

  1. to discharge urine : micturate

urine ['yər-ən, 'yu̇r-] -n, adj

  1. waste material that is secreted by the kidney in vertebrates, is rich in end products of protein metabolism together with salts and pigments, and forms a clear amber and usu. slightly acid fluid in mammals but is semisolid in birds and reptiles

uri·no·gen·i·tal [,yu̇r-ə-nō-'je-nə-tᵊl] -adj

  1. urogenital

uri·nom·e·ter [,yu̇r-ə-'nä-mə-tər] -n

  1. a small hydrometer for determining the specific gravity of urine

URL [,yü-(,)är-'el, 'ər(-ə)l] -n

  1. the address of a resource (as a document or Web site) on the Internet that consists of a communications protocol followed by the name or address of a computer on the network and that often includes additional locating information (as directory and file names)
    • our site's URL is http://www.Merriam-Webster.com
    called also uniform resource locator universal resource locator

urn ['ərn] -n

  1. a vessel that is typically an ornamental vase on a pedestal and that is used for various purposes (as preserving the ashes of the dead after cremation)
  2. a closed vessel usu. with a spigot for serving a hot beverage
    • a coffee urn

uro·ca·nic acid [,yu̇r-ə-'kā-nik-, -'ka-] -n

  1. a crystalline acid C 6H 6N 2O 2that is normally present in human skin

uro·chor·date [,yu̇r-ə-'kȯr-dət, -,dāt] -n, adj

  1. tunicate

uro·chrome ['yu̇r-ə-,krōm] -n

  1. a yellow pigment to which the color of normal urine is principally due

uro·dele ['yu̇r-ə-,dēl] -n, adj

  1. any of an order (Caudata syn. Urodela) of amphibians (as newts and salamanders) that have a tail throughout life

uro·gen·i·tal [,yu̇r-ō-'je-nə-tᵊl] -adj

  1. of, relating to, or being the organs or functions of excretion and reproduction

uro·gy·ne·col·o·gy [,yu̇r-ō-,gī-nə-'kä-lə-jē, -,ji-] -n

  1. a branch of medicine concerned with urological problems affecting women

uro·ki·nase [,yu̇r-ō-'kī-,nās, -,nāz] -n

  1. an enzyme that is produced by the kidney and found in urine, that activates plasminogen, and that is used therapeutically to dissolve blood clots (as in the heart)

uro·lith ['yu̇r-ə-,lith] -n

  1. a calculus in the urinary tract

uro·lith·ia·sis [,yu̇r-ə-li-'thī-ə-səs] -n

  1. a condition that is marked by the formation or presence of calculi in the urinary tract

uro·logi·cal [,yu̇r-ə-'lä-ji-kəl] -adj

  1. of or relating to the urinary tract or to urology

urol·o·gist [yu̇-'rä-lə-jist] -n

  1. a physician who specializes in the urinary or urogenital tract

uron·ic acid [yu̇-'rä-nik-] -n

  1. any of a class of acidic compounds of the general formula HOOC(CHOH) n CHO that contain both carboxylic and aldehydic groups, are oxidation products of sugars, and occur combined in many polysaccharides and in urine

uro·pod ['yu̇r-ə-,päd] -n

  1. either of the flattened lateral appendages of the last abdominal segment of a crustacean
  2. an abdominal appendage of a crustacean

uro·py·gi·al gland [,yu̇r-ə-'pī-jē-əl-] -n

  1. a large gland that occurs in most birds, opens dorsally at the base of the tail feathers, and usu. secretes an oily fluid which the bird uses in preening its feathers called also oil gland

uro·py·gi·um [,yu̇r-ə-'pī-jē-əm] -n

  1. the fleshy and bony prominence at the posterior extremity of a bird's body that supports the tail feathers

uro·style ['yu̇r-ə-,stī(-ə)l] -n

  1. a long unsegmented bone that represents a number of fused vertebrae and forms the posterior part of the vertebral column of frogs and toads

Ur·sa Ma·jor [,ər-sə-'mā-jər] -n

  1. a constellation that is the most conspicuous of the northern constellations, is situated near the north pole of the heavens, and contains the stars forming the Big Dipper two of which are in a line indicating the direction of the North Star called also Great Bear

Ursa Mi·nor [-'mī-nər] -n

  1. a constellation that includes the north pole of the heavens and the stars which form the Little Dipper with the North Star at the tip of the handle called also Little Bear

ur·sine ['ər-,sīn] -adj

  1. of or relating to a bear or the bear family (Ursidae)
  2. suggesting or characteristic of a bear
    • a lumbering ursine gait

Ur·su·line ['ər-sə-lən, -,līn, -,lēn] -n

  1. a member of any of several Roman Catholic teaching orders of nuns
  2. a member of a teaching order founded by St. Angela Merici in Brescia, Italy, in 1535

ur·text ['u̇r-,tekst] -n

  1. the original text (as of a musical score)

ur·ti·car·ia [,ər-tə-'ker-ē-ə] -n, adj

  1. hives

ur·ti·cate ['ər-tə-,kāt] -vi, n

  1. to produce wheals or itching
  2. to induce hives

urus ['yu̇r-əs] -n

  1. aurochs

uru·shi·ol [yu̇-'rü-shē-,ȯl, u̇-', -,ōl] -n

  1. a mixture of catechol derivatives with saturated or unsaturated side chains of 15 or 17 carbon atoms that is an oily toxic irritant principle present in poison ivy and some related plants (genus Rhus) and in lacquers derived from such plants