The Collaborative International Dictionary of English v.0.48:

Contemn \Con*temn"\ (k[o^]n*t[e^]m"), v. t. [imp. & p. p.
   Contemned (-t[e^]md); p. pr. & vb. n. Contemning
   (-t[e^]m"n[i^]ng or -t[e^]m"[i^]ng).] [L. contemnere,
   -temptum; con- + temnere to slight, despise: cf. OF.
   contemner.]
   To view or treat with contempt, as mean and despicable; to
   reject with disdain; to despise; to scorn.
   [1913 Webster]

         Thy pompous delicacies I contemn.        --Milton.
   [1913 Webster]

         One who contemned divine and human laws. --Dryden.

   Syn: To despise; scorn; disdain; spurn; slight; neglect;
        underrate; overlook.

   Usage: To Contemn, Despise, Scorn, Disdain. Contemn
          is the generic term, and is applied especially to
          objects, qualities, etc., which are deemed
          contemptible, and but rarely to individuals; to
          despise is to regard or treat as mean, unbecoming, or
          worthless; to scorn is stronger, expressing a quick,
          indignant contempt; disdain is still stronger,
          denoting either unwarrantable pride and haughtiness or
          an abhorrence of what is base.
          [1913 Webster]

WordNet (r) 3.0 (2006):

contemn
    v 1: look down on with disdain; "He despises the people he has
         to work for"; "The professor scorns the students who don't
         catch on immediately" [syn: contemn, despise, scorn,
         disdain]

Moby Thesaurus II by Grady Ward, 1.0:

66 Moby Thesaurus words for "contemn":
   abhor, abjure, be above, be contemptuous of, brush aside,
   care nothing for, chuck, chuck out, contradict, decline, deny,
   deride, despise, disapprove, discard, disclaim, discount, disdain,
   dismiss, disown, disparage, disprize, disregard, dump on, except,
   exclude, feel contempt for, feel superior to, forswear,
   hold beneath one, hold cheap, hold in contempt, ignore, insult,
   look down upon, misprize, pass by, pass up, push aside, put down,
   rank low, rebuff, recant, refuse, refuse to consider, reject,
   renounce, repel, repudiate, repulse, ridicule, scorn, scout,
   set at naught, shove away, sneer at, sneeze at, sniff at, snort at,
   spurn, think nothing of, throw away, throw out, turn away,
   turn out, waive