The Collaborative International Dictionary of English v.0.48:

Dire \Dire\ (d[imac]r), a. [Compar. Direr (d[imac]r"[~e]r);
   superl. Direst.] [L. dirus; of uncertain origin.]
   1. Ill-boding; portentous; as, dire omens.
      [1913 Webster]

   2. Evil in great degree; dreadful; dismal; horrible;
      terrible; lamentable.
      [1913 Webster]

            Dire was the tossing, deep the groans. --Milton.
      [1913 Webster]

            Gorgons and hydras and chimeras dire. --Milton.
      [1913 Webster]

WordNet (r) 3.0 (2006):

dire
    adj 1: fraught with extreme danger; nearly hopeless; "a
           desperate illness"; "on all fronts the Allies were in a
           desperate situation due to lack of materiel"-
           G.C.Marshall; "a dire emergency" [syn: desperate,
           dire]
    2: causing fear or dread or terror; "the awful war"; "an awful
       risk"; "dire news"; "a career or vengeance so direful that
       London was shocked"; "the dread presence of the headmaster";
       "polio is no longer the dreaded disease it once was"; "a
       dreadful storm"; "a fearful howling"; "horrendous explosions
       shook the city"; "a terrible curse" [syn: awful, dire,
       direful, dread(a), dreaded, dreadful, fearful,
       fearsome, frightening, horrendous, horrific,
       terrible]

Moby Thesaurus II by Grady Ward, 1.0:

173 Moby Thesaurus words for "dire":
   abominable, apocalyptic, appalling, arrant, astounding, atrocious,
   awe-inspiring, awesome, awful, bad, badly off, baleful, baneful,
   base, beastly, beneath contempt, black, blameworthy, bodeful,
   boding, brutal, burning, calamitous, cataclysmal, cataclysmic,
   catastrophic, clamant, clamorous, climacteric, contemptible,
   critical, crucial, crying, dark, deplorable, depressed, depressing,
   desperate, despicable, destructive, detestable, direful,
   disastrous, disgusting, distressing, donsie, doomful, dread,
   dreaded, dreadful, dreary, egregious, enormous, evil, evil-starred,
   exigent, fatal, fateful, fell, fetid, filthy, flagrant, foreboding,
   formidable, fortuneless, foul, frightful, fulsome, funest, ghastly,
   ghoulish, gloomy, grievous, grim, grisly, gross, gruesome, hapless,
   hateful, heartbreaking, heinous, hideous, horrendous, horrible,
   horrid, horrific, horrifying, ill, ill off, ill-boding, ill-fated,
   ill-omened, ill-starred, imperative, importunate,
   in adverse circumstances, inauspicious, infamous, instant,
   lamentable, loathsome, lousy, lowering, luckless, macabre,
   menacing, monstrous, morbid, nasty, nefarious, noisome, notorious,
   obnoxious, odious, of evil portent, offensive, ominous,
   out of luck, outrageous, pitiable, pitiful, planet-struck,
   portending, portentous, rank, redoubtable, regrettable,
   reprehensible, repulsive, rotten, ruinous, sad, scandalous,
   schlock, schrecklich, scurvy, shabby, shameful, shocking, shoddy,
   short of luck, sinister, somber, sordid, squalid, star-crossed,
   terrible, terrific, threatening, too bad, tragic, tremendous,
   unblessed, unclean, underprivileged, unfavorable, unfortunate,
   unhappy, unlucky, unpromising, unpropitious, unprosperous,
   unprovidential, unspeakable, untoward, urgent, vile, villainous,
   woeful, worst, worthless, wreckful, wretched