The Collaborative International Dictionary of English v.0.48:

Orgiastic \Or`gi*as"tic\, a. [Gr. ?. See Orgy.]
   Pertaining to, or of the nature of, orgies. --Elton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

orgiastic
    adj 1: used of frenzied sexual activity
    2: used of riotously drunken merrymaking; "a night of
       bacchanalian revelry"; "carousing bands of drunken soldiers";
       "orgiastic festivity" [syn: bacchanalian, bacchanal,
       bacchic, carousing, orgiastic]

Moby Thesaurus II by Grady Ward, 1.0:

76 Moby Thesaurus words for "orgiastic":
   Adamic, Circean, abandoned, amok, animal, animalistic, beastlike,
   beastly, bellowing, berserk, bestial, bodily, brutal, brute,
   brutish, carnal, carnal-minded, carried away, coarse, corybantic,
   delirious, demoniac, distracted, earthy, ecstatic, enraptured,
   fallen, feral, ferocious, fierce, fleshly, frantic, frenzied,
   fulminating, furious, gross, haggard, hog-wild, howling,
   hysterical, in a transport, in hysterics, incontinent, intemperate,
   intoxicated, lapsed, mad, madding, maniac, material, materialistic,
   nonspiritual, orgasmic, physical, possessed, postlapsarian, rabid,
   raging, ramping, ranting, raving, ravished, roaring, running mad,
   saturnalian, storming, swinish, transported, uncontinent,
   uncontrollable, unrestrained, unspiritual, violent, wild,
   wild-eyed, wild-looking