[syn: hideous, repulsive]
The Collaborative International Dictionary of English v.0.48:
Hideous \Hid"e*ous\ (h[i^]d"[-e]*[u^]s; 277), a. [OE. hidous,
   OF. hidous, hidos, hidus, hisdos, hisdous, F. hideux: cf. OF.
   hide, hisde, fright; of uncertain origin; cf. OHG. egid[imac]
   horror, or L. hispidosus, for hispidus rough, bristly, E.
   hispid.]
   1. Frightful, shocking, or offensive to the eyes; dreadful to
      behold; as, a hideous monster; hideous looks. "A piteous
      and hideous spectacle." --Macaulay.
      [1913 Webster]
   2. Distressing or offensive to the ear; exciting terror or
      dismay; as, a hideous noise. "Hideous cries." --Shak.
      [1913 Webster]
   3. Hateful; shocking. "Sure, you have some hideous matter to
      deliver." --Shak.
   Syn: Frightful; ghastly; grim; grisly; horrid; dreadful;
        terrible. -- Hid"e*ous*ly, adv. -- Hid"e*ous*ness,
        n.
        [1913 Webster]
WordNet (r) 3.0 (2006):
hideous
    adj 1: grossly offensive to decency or morality; causing horror;
           "subjected to outrageous cruelty"; "a hideous pattern of
           injustice"; "horrific conditions in the mining industry"
           [syn: hideous, horrid, horrific, outrageous]
    2: so extremely ugly as to be terrifying; "a hideous scar"; "a
       repulsive mask" [syn: hideous, repulsive]
Moby Thesaurus II by Grady Ward, 1.0:
77 Moby Thesaurus words for "hideous":
   abhorrent, abominable, appalling, astounding, atrocious,
   awe-inspiring, awesome, awful, baneful, beastly, contemptible,
   damnable, dire, direful, disgusting, dread, dreaded, dreadful,
   exceptionable, execrable, fell, forbidding, formidable, foul,
   frightful, ghastly, ghoulish, grim, grisly, grotesque, gruesome,
   hateful, heinous, horrendous, horrible, horrid, horrific,
   horrifying, ill-favored, ill-looking, inadmissible, loathsome,
   lurid, macabre, monstrous, morbid, nasty, nauseating, nauseous,
   odious, offensive, outrageous, redoubtable, repellent, repelling,
   repugnant, repulsive, revolting, rotten, schrecklich, shocking,
   sickening, terrible, terrific, terrifying, tragic, tremendous,
   ugly, unacceptable, unbeautiful, uncomely, undesirable, unsightly,
   unspeakable, unwanted, unwelcome, vile