The Collaborative International Dictionary of English v.0.48:

Contemptible \Con*tempt"i*ble\, a.
   1. Worthy of contempt; deserving of scorn or disdain; mean;
      vile; despicable. --Milton.
      [1913 Webster]

            The arguments of tyranny are ascontemptible as its
            force is dreadful.                    --Burke.
      [1913 Webster]

   2. Despised; scorned; neglected; abject. --Locke.
      [1913 Webster]

   3. Insolent; scornful; contemptuous. [Obs.]
      [1913 Webster]

            If she should make tender of her love, 't is very
            possible he 'll scorn it; for the man . . . hath a
            contemptible spirit.                  --Shak.

   Syn: Despicable; abject; vile; mean; base; paltry; worthless;
        sorry; pitiful; scurrile. See Contemptuous.

   Usage: Contemptible, Despicable, Pitiful, Paltry.
          Despicable is stronger than contemptible, as despise
          is stronger than contemn. It implies keen
          disapprobation, with a mixture of anger. A man is
          despicable chiefly for low actions which mark his
          life, such as servility, baseness, or mean adulation.
          A man is contemptible for mean qualities which
          distinguish his character, especially those which show
          him to be weak, foolish, or worthless. Treachery is
          despicable, egotism is contemptible. Pitiful and
          paltry are applied to cases which are beneath anger,
          and are simply contemptible in a high degree.
          [1913 Webster]

WordNet (r) 3.0 (2006):

contemptible
    adj 1: deserving of contempt or scorn [ant: estimable]

Moby Thesaurus II by Grady Ward, 1.0:

136 Moby Thesaurus words for "contemptible":
   abhorrent, abject, abominable, arrant, atrocious, awful, bad, base,
   beastly, beggarly, below contempt, beneath contempt, blameworthy,
   brutal, cheap, cheesy, common, crude, crummy, debased, degraded,
   deplorable, depraved, despicable, detestable, dire, dirty,
   disgusting, dreadful, egregious, enormous, execrable, fetid,
   filthy, flagrant, forbidding, foul, fulsome, gaudy, gimcracky,
   grave, grievous, gross, hateful, heinous, horrible, horrid,
   ignoble, ignominious, infamous, inferior, lamentable, little,
   loathsome, lousy, low, low-down, lumpen, malodorous, mangy, mean,
   measly, mephitic, meretricious, miasmal, miasmic, miserable,
   monstrous, nasty, nauseating, nefarious, noisome, notorious,
   noxious, objectionable, obnoxious, obscene, odious, offensive,
   outcast, outrageous, paltry, pathetic, petty, pitiable, pitiful,
   poky, poor, rank, rebarbative, regrettable, repellent,
   reprehensible, reptilian, repugnant, repulsive, revolting, rotten,
   rubbishy, sad, scabby, scandalous, schlock, scrubby, scruffy,
   scummy, scurvy, scuzzy, shabby, shameful, shocking, shoddy,
   sickening, small, sordid, sorry, squalid, stinking, terrible,
   too bad, trashy, trumpery, two-for-a-cent, two-for-a-penny,
   twopenny, twopenny-halfpenny, unclean, unmentionable, unworthy,
   valueless, vile, villainous, woeful, worst, worthless, wretched