The Collaborative International Dictionary of English v.0.48:

Contrast \Con"trast\ (k[o^]n"tr[.a]st), n. [F. contraste: cf.
   It. contrasto.]
   1. The act of contrasting, or the state of being contrasted;
      comparison by contrariety of qualities.
      [1913 Webster]

            place the prospect of the soul
            In sober contrast with reality.       --Wordsworth.
      [1913 Webster]

   2. Opposition or dissimilitude of things or qualities;
      unlikeness, esp. as shown by juxtaposition or comparison.
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            The contrasts and resemblances of the seasons.
                                                  --Whewell.
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   3. (Fine Arts) The opposition of varied forms, colors, etc.,
      which by such juxtaposition more vividly express each
      other's peculiarities.                      --Fairholt.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Contrast \Con*trast"\, v. i. [imp. & p. p. Contrasted; p. pr.
   & vb. n. Contrasting.] [F. contraster, LL. contrastare to
   resist, withstand, fr. L. contra + stare to stand. See
   Stand.]
   To stand in opposition; to exhibit difference, unlikeness, or
   opposition of qualities.
   [1913 Webster]

         The joints which divide the sandstone contrast finely
         with the divisional planes which separate the basalt
         into pillars.                            --Lyell.
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The Collaborative International Dictionary of English v.0.48:

Contrast \Con*trast"\, v. t.
   1. To set in opposition, or over against, in order to show
      the differences between, or the comparative excellences
      and defects of; to compare by difference or contrariety of
      qualities; as, to contrast the present with the past.
      [1913 Webster]

   2. (Fine Arts) To give greater effect to, as to a figure or
      other object, by putting it in some relation of opposition
      to another figure or object.
      [1913 Webster]

            the figures of the groups must not be all on side .
            . . but must contrast each other by their several
            position.                             --Dryden.
      [1913 Webster]

WordNet (r) 3.0 (2006):

contrast
    n 1: the opposition or dissimilarity of things that are
         compared; "in contrast to", "by contrast" [syn: contrast,
         direct contrast]
    2: the act of distinguishing by comparing differences
    3: a conceptual separation or distinction; "there is a narrow
       line between sanity and insanity" [syn: line, dividing
       line, demarcation, contrast]
    4: the perceptual effect of the juxtaposition of very different
       colors
    5: the range of optical density and tone on a photographic
       negative or print (or the extent to which adjacent areas on a
       television screen differ in brightness)
    v 1: put in opposition to show or emphasize differences; "The
         middle school teacher contrasted her best student's work
         with that of her weakest student"
    2: to show differences when compared; be different; "the
       students contrast considerably in their artistic abilities"
       [syn: contrast, counterpoint]

Moby Thesaurus II by Grady Ward, 1.0:

194 Moby Thesaurus words for "contrast":
   allegory, analogize, analogy, antagonism, anteposition, antipathy,
   antithesis, arc lighting, assimilate, bad copy, bad likeness,
   balance, balancing, black and white, bracket, bring into analogy,
   bring into comparison, bump heads, camouflage, chiaroscuro,
   clashing, collate, collision, comparative anatomy,
   comparative degree, comparative grammar, comparative judgment,
   comparative linguistics, comparative literature,
   comparative method, compare, compare and contrast, compare with,
   comparing, comparison, conflict, confront, confrontation,
   confrontment, contend, contention, contradiction,
   contradistinction, contraindication, contrapose, contraposit,
   contraposition, contrariety, contrastiveness, correlation,
   counteract, counterpose, counterposition, cross-purposes,
   decorative lighting, departure, deviation, difference,
   differentiate, direct lighting, disaccord, disaccordance,
   disagreement, disconformity, discongruity, discordance,
   discrepancy, discreteness, discriminate, disguise, disparity,
   dissemblance, dissent, dissimilarity, dissimilation, dissimilitude,
   dissonance, distinction, distinctiveness, distinctness,
   distinguish, divergence, divergency, diversity, draw a comparison,
   draw a parallel, electric lighting, enlightenment, face, far cry,
   festoon lighting, floodlighting, fluorescent lighting, front,
   gaslighting, glow lighting, heterogeneity, highlights, hostility,
   illumination, inaccordance, incandescent lighting,
   incommensurability, incomparability, incompatibility, incongruity,
   inconsistency, inconsonance, indirect lighting, inequality,
   inharmoniousness, inharmony, inimicalness, irradiation,
   irreconcilability, juxtapose, lie opposite, light and shade,
   lighting, liken, liken to, likening, makeup, match, matching,
   measure against, meet head-on, mere caricature, metaphor,
   metaphorize, mixture, nonconformity, nonuniformity, odds, oppose,
   opposing, oppositeness, opposition, opposure, oppugnance,
   oppugnancy, otherness, overhead lighting, parallel, parallelism,
   perversity, place against, polar opposition, polarity,
   polarization, polarize, poor imitation, pose against,
   posing against, proportion, put in opposition, radiation, relate,
   relation, repugnance, run a comparison, separateness, set against,
   set in contrast, set in opposition, set off, set off against,
   set over against, showdown, simile, similitude, similize,
   spot lighting, stage lighting, stand opposed, stand opposite,
   strip lighting, subtend, tonality, trope of comparison,
   unconformity, unlikeness, unorthodoxy, unresemblance, unsameness,
   unsimilarity, variance, variation, variegation, variety,
   view together, weigh, weigh against, weighing