The Collaborative International Dictionary of English v.0.48:

Wart \Wart\, n. [OE. werte, AS. wearte; akin to D. wrat, G.
   warze, OHG. warza, Icel. varta, Sw. v[*a]rta, Dan. vorte;
   perh. orig., a growth, and akin to E. wort; or cf. L. verruca
   wart.]
   [1913 Webster]
   1. (Med.) A small, usually hard, tumor on the skin formed by
      enlargement of its vascular papillae, and thickening of
      the epidermis which covers them.
      [1913 Webster]

   2. An excrescence or protuberance more or less resembling a
      true wart; specifically (Bot.), a glandular excrescence or
      hardened protuberance on plants.
      [1913 Webster]

   Fig wart, Moist wart (Med.), a soft, bright red, pointed
      or tufted tumor found about the genitals, often massed
      into groups of large size. It is a variety of condyloma.
      Called also pointed wart, venereal wart. --L. A.
      Duhring.

   Wart cress (Bot.), the swine's cress. See under Swine.

   Wart snake (Zool.), any one of several species of East
      Indian colubrine snakes of the genus Acrochordus, having
      the body covered with wartlike tubercles or spinose
      scales, and lacking cephalic plates and ventral scutes.

   Wart spurge (Bot.), a kind of wartwort (Euphorbia
      Helioscopia).
      [1913 Webster]

WordNet (r) 3.0 (2006):

wart
    n 1: any small rounded protuberance (as on certain plants or
         animals)
    2: an imperfection in someone or something that is suggestive of
       a wart (especially in smallness or unattractiveness)
    3: (pathology) a firm abnormal elevated blemish on the skin;
       caused by a virus [syn: wart, verruca]

Moby Thesaurus II by Grady Ward, 1.0:

163 Moby Thesaurus words for "wart":
   Lilliputian, Tom Thumb, bantam, banty, benign tumor, bilge,
   birthmark, blackhead, blain, bleb, blemish, blister, blob, boss,
   bow, brownie, bubble, bulb, bulge, bulla, bump, bunch, burl,
   button, cahot, callosity, callus, cancer, carcinoma, check, chine,
   chit, cicatrix, clump, comedo, condyle, convex, corn, crack,
   crater, craze, cyst, defacement, defect, deformation, deformity,
   diminutive, disfiguration, disfigurement, distortion, dowel, dwarf,
   ear, elf, excrescence, fault, featherweight, fingerling, flange,
   flap, flaw, freckle, fungosity, fungus, gall, gnarl, gnome, growth,
   handle, hemangioma, hickey, hill, homunculus, hump, hunch,
   intumescence, jog, joggle, keloid, kink, knob, knot, knur, knurl,
   lentigo, lightweight, lip, loop, lump, malignant growth, manikin,
   metastatic tumor, midge, midget, milium, mini, minikin, minnow,
   minny, mole, morbid growth, mountain, mouse, needle scar, neoplasm,
   nevus, nonmalignant tumor, nub, nubbin, nubble, outgrowth,
   papilloma, peewee, peg, pimple, pip-squeak, pit, pock, pockmark,
   pony, port-wine mark, port-wine stain, proud flesh, pustule, pygmy,
   rib, ridge, rift, ring, runt, sarcoma, scab, scar, scratch,
   sebaceous cyst, shoulder, shrimp, slip, small fry, snip, snippet,
   spine, split, strawberry mark, stud, sty, style, tab, tit, track,
   tubercle, tubercule, tumor, twist, verruca, vesicle, wale, warp,
   weal, welt, wen, whitehead, wisp



The Jargon File (version 4.4.7, 29 Dec 2003):

wart
 n.

    A small, crocky feature that sticks out of an otherwise clean design.
    Something conspicuous for localized ugliness, especially a special-case
    exception to a general rule. For example, in some versions of csh(1),
    single quotes literalize every character inside them except !. In ANSI C,
    the ?? syntax used for obtaining ASCII characters in a foreign environment
    is a wart. See also miswart.


The Free On-line Dictionary of Computing (30 December 2018):

wart

   A small, crocky feature that sticks out of an otherwise
   clean design.  Something conspicuous for localised ugliness,
   especially a special-case exception to a general rule.  For
   example, in some versions of "csh(1)", single quotes
   literalise every character inside them except "!".  In ANSI C,
   the "?" syntax used for obtaining ASCII characters in a
   foreign environment is a wart.  See also miswart.

   [Jargon File]