The Collaborative International Dictionary of English v.0.48:

Contemptuous \Con*temp"tu*ous\ (?; 135), a.
   Manifesting or expressing contempt or disdain; scornful;
   haughty; insolent; disdainful.
   [1913 Webster]

         A proud, contemptuous behavior.          --Hammond.
   [1913 Webster]

         Savage invective and contemptuous sarcasm. --Macaulay.
   [1913 Webster]

         Rome . . . entertained the most contemptuous opinion of
         the Jews.                                --Atterbury.

   Syn: Scornful; insolent; haughty; disdainful; supercilious;
        insulting; contumelious.

   Usage: Contemptuous, Contemptible. These words, from
          their similarity of sound, are sometimes erroneously
          interchanged, as when a person speaks of having "a
          very contemptible opinion of another." Contemptible is
          applied to that which is the object of contempt; as,
          contemptible conduct; acontemptible fellow.
          Contemptuous is applied to that which indicates
          contempt; as, a contemptuous look; a contemptuous
          remark; contemptuous treatment. A person, or whatever
          is personal, as an action, an expression, a feeling,
          an opinion, may be either contemptuous or
          contemptible; a thing may be contemptible, but can not
          be contemptuous.
          [1913 Webster]

WordNet (r) 3.0 (2006):

contemptuous
    adj 1: expressing extreme contempt [syn: contemptuous,
           disdainful, insulting, scornful]

Moby Thesaurus II by Grady Ward, 1.0:

113 Moby Thesaurus words for "contemptuous":
   abjuratory, abusive, arrogant, audacious, back-biting, belittling,
   biggety, bitchy, blackening, blameful, bluff, bold, brash, brassy,
   brazen, bumptious, calumniatory, calumnious, catty, cavalier,
   censorious, challenging, cheeky, chutzpadik, clannish, cliquish,
   cocky, condemnatory, contumelious, crusty, damnatory, daring,
   declinatory, defamatory, defiant, defying, denunciatory,
   deprecative, deprecatory, depreciative, depreciatory, derisive,
   derisory, derogative, derogatory, despising, detractory,
   disdainful, dismissive, disparaging, disregardful, disrespectful,
   exclusive, execrating, execrative, execratory, facy, flip,
   flippant, fresh, gally, gratuitous, greatly daring, haughty,
   impertinent, impudent, insolent, insulting, invective, inveighing,
   judgmental, libelous, malapert, minimizing, nervy, objurgatory,
   pejorative, pert, priggish, regardless of consequences, rejective,
   renunciative, reproachful, reprobative, reviling, ridiculing, rude,
   sassy, saucy, scandalous, scoffing, scornful, scurrile, scurrilous,
   slanderous, slighting, smart, smart-alecky, smart-ass, sneering,
   sniffy, snobbish, snobby, snooty, snotty, supercilious,
   toploftical, toplofty, uncalled-for, vilifying, vituperative,
   wise-ass, withering