The Collaborative International Dictionary of English v.0.48:

Horrid \Hor"rid\, a. [L. horridus. See Horror, and cf.
   Ordure.]
   1. Rough; rugged; bristling. [Archaic]
      [1913 Webster]

            Horrid with fern, and intricate with thorn.
                                                  --Dryden.
      [1913 Webster]

   2. Fitted to excite horror; dreadful; hideous; shocking;
      hence, very offensive.
      [1913 Webster]

            Not in the legions
            Of horrid hell.                       --Shak.
      [1913 Webster]

            The horrid things they say.           --Pope.

   Syn: Frightful; hideous; alarming; shocking; dreadful; awful;
        terrific; horrible; abominable.
        [1913 Webster]

WordNet (r) 3.0 (2006):

horrid
    adj 1: exceedingly bad; "when she was bad she was horrid"
    2: 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]

Moby Thesaurus II by Grady Ward, 1.0:

103 Moby Thesaurus words for "horrid":
   abhorrent, abominable, appalling, arrant, astounding, atrocious,
   awe-inspiring, awesome, awful, baneful, base, beastly,
   beneath contempt, blameworthy, brutal, contemptible, deplorable,
   despicable, detestable, dire, direful, disgusting, dread, dreaded,
   dreadful, egregious, enormous, fell, fetid, filthy, flagrant,
   forbidding, formidable, foul, frightful, fulsome, ghastly,
   ghoulish, grievous, grim, grisly, gross, gruesome, hateful,
   heinous, hideous, horrendous, horrible, horrific, horrifying,
   infamous, lamentable, loathsome, lousy, lurid, macabre, monstrous,
   morbid, nasty, nefarious, noisome, notorious, obnoxious, odious,
   offensive, outrageous, pitiable, pitiful, rank, redoubtable,
   regrettable, repellent, repelling, reprehensible, repugnant,
   repulsive, revolting, rotten, sad, scandalous, schlock,
   schrecklich, scurvy, shabby, shameful, shocking, shoddy, sordid,
   squalid, terrible, terrific, terrifying, too bad, tragic,
   tremendous, unclean, unspeakable, vile, villainous, woeful, worst,
   worthless, wretched