The Collaborative International Dictionary of English v.0.48:

Abominable \A*bom"i*na*ble\, a. [F. abominable. L. abominalis.
   See Abominate.]
   1. Worthy of, or causing, abhorrence, as a thing of evil
      omen; odious in the utmost degree; very hateful;
      detestable; loathsome; execrable.
      [1913 Webster]

   2. Excessive; large; -- used as an intensive. [Obs.]
      [1913 Webster]

   Note: Juliana Berners . . . informs us that in her time [15th
         c.], "abomynable syght of monkes" was elegant English
         for "a large company of friars." --G. P. Marsh.
         [1913 Webster]

WordNet (r) 3.0 (2006):

abominable
    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]
    2: exceptionally bad or displeasing; "atrocious taste";
       "abominable workmanship"; "an awful voice"; "dreadful
       manners"; "a painful performance"; "terrible handwriting";
       "an unspeakable odor came sweeping into the room" [syn:
       atrocious, abominable, awful, dreadful, painful,
       terrible, unspeakable]

Moby Thesaurus II by Grady Ward, 1.0:

171 Moby Thesaurus words for "abominable":
   aberrant, abhorrent, abject, abnormal, accursed, arrant, atrocious,
   awful, bad, base, beastly, beggarly, below contempt,
   beneath contempt, black, blamable, blameworthy, brutal, cheesy,
   contemptible, criminal, crude, crummy, cursed, damnable, dark,
   debased, degraded, delinquent, deplorable, depraved, despicable,
   detestable, deviant, dire, dirty, disagreeable, disgraceful,
   disgusting, distasteful, dreadful, egregious, enormous, evil,
   execrable, fetid, filthy, flagitious, flagrant, forbidding, foul,
   frightful, fulsome, grave, grievous, gross, hardly the thing,
   hateful, heinous, horrible, horrid, ignoble, ignominious, illegal,
   improper, in bad taste, inappropriate, incorrect, indecorous,
   infamous, iniquitous, knavish, lamentable, little, loathsome,
   lousy, low, low-down, lumpen, malodorous, mangy, mean, measly,
   mephitic, miasmal, miasmic, miserable, monstrous, nasty, naughty,
   nauseating, nauseous, nefarious, noisome, not done, not the thing,
   notorious, noxious, objectionable, obnoxious, obscene, odious,
   off-base, off-color, offensive, out-of-line, outrageous, paltry,
   peccant, petty, pitiable, pitiful, poky, poor, rank, rebarbative,
   regrettable, repellent, reprehensible, reprobate, reptilian,
   repugnant, repulsive, revolting, rotten, sacrilegious, sad, scabby,
   scandalous, schlock, scrubby, scruffy, scummy, scurvy, shabby,
   shameful, shameless, shocking, shoddy, sickening, sinful, small,
   sordid, squalid, stinking, terrible, too bad, unclean, undue,
   unfit, unfitting, unforgivable, unlawful, unmentionable,
   unpardonable, unpleasant, unrighteous, unseemly, unspeakable,
   unsuitable, unworthy, vicious, vile, villainous, wicked, woeful,
   worst, worthless, wretched, wrong, wrongful