The Collaborative International Dictionary of English v.0.48:

Odious \O"di*ous\, a. [L. odiosus, from odium hatred: cf. F.
   odieux. See Odium.]
   1. Hateful; deserving or receiving hatred; as, an odious
      name, system, vice. "All wickedness will be most odious."
      --Sprat.
      [1913 Webster]

            He rendered himself odious to the Parliament.
                                                  --Clarendon.
      [1913 Webster]

   2. Causing or provoking hatred, repugnance, or disgust;
      offensive; disagreeable; repulsive; as, an odious sight;
      an odious smell. --Milton.
      [1913 Webster]

            The odious side of that polity.       --Macaulay.
      [1913 Webster]

   Syn: Hateful; detestable; abominable; disgusting; loathsome;
        invidious; repulsive; forbidding; unpopular.
        [1913 Webster] -- O"di*ous`ly. adv. --
        O"di*ous*ness, n.
        [1913 Webster]

WordNet (r) 3.0 (2006):

odious
    adj 1: unequivocally detestable; "abominable treatment of
           prisoners"; "detestable vices"; "execrable crimes";
           "consequences odious to those you govern"- Edmund Burke
           [syn: abominable, detestable, execrable, odious]

Moby Thesaurus II by Grady Ward, 1.0:

150 Moby Thesaurus words for "odious":
   abhorrent, abject, abominable, arrant, atrocious, awful, barfy,
   base, beastly, beggarly, below contempt, beneath contempt,
   blameworthy, brutal, cheesy, contemptible, crappy, crude, crummy,
   debased, degraded, deplorable, depraved, despicable, detestable,
   dire, dirty, disgusting, dislikable, displeasing, distasteful,
   dreadful, egregious, enormous, execrable, fecal, feculent, fetid,
   filthy, flagrant, flyblown, forbidding, foul, fulsome, gloppy,
   grave, grievous, gross, gunky, hateful, heinous, horrible, horrid,
   icky, ignoble, infamous, intolerable, lamentable, little,
   loathsome, lousy, low, low-down, lumpen, maggoty, malodorous,
   mangy, mean, measly, mephitic, miasmal, miasmic, miserable,
   mislikable, monstrous, mucky, nasty, nauseating, nefarious,
   noisome, notorious, noxious, objectionable, obnoxious, obscene,
   offensive, ordurous, outrageous, paltry, petty, pitiable, pitiful,
   poky, poor, puky, putrid, rank, rebarbative, regrettable,
   repellent, reprehensible, reptilian, repugnant, repulsive,
   revolting, rotten, sad, scabby, scandalous, schlock, scrubby,
   scruffy, scummy, scurfy, scurvy, shabby, shameful, shitty,
   shocking, shoddy, sickening, slabby, slimy, sloppy, sloshy, sludgy,
   slushy, small, sordid, sposhy, squalid, stinking, terrible,
   too bad, unclean, uncongenial, uninviting, unlikable, unlovable,
   unmentionable, unpleasant, vile, villainous, vomity, woeful, wormy,
   worst, worthless, wretched, yecchy