The Collaborative International Dictionary of English v.0.48:

Crass \Crass\ (kr?s), a. [L. crassus thick, fat, gross, prob.
   orig., closely woven. See Grease animal fat, and cf.
   Crate, Hurdle.]
   Gross; thick; dense; coarse; not elaborated or refined.
   "Crass and fumid exhalations." --Sir. T. Browne. "Crass
   ignorance" --Cudworth.
   [1913 Webster] Crassament

WordNet (r) 3.0 (2006):

crass
    adj 1: (of persons) so unrefined as to be lacking in
           discrimination and sensibility

Moby Thesaurus II by Grady Ward, 1.0:

98 Moby Thesaurus words for "crass":
   Boeotian, absolute, arrant, asinine, beef-brained, beef-witted,
   blockish, bovine, broad-bodied, bulky, bullnecked, chumpish,
   churlish, classical, cloddish, coarse, complete, consummate,
   corpulent, cowish, crude, decided, definitive, dense, doltish,
   downright, dullard, dumb, duncical, duncish, earthy, egregious,
   fat, flagrant, full, full-bodied, gaudy, glaring, gross, heavy,
   heavyset, ineducable, inelegant, intolerable, klutzy, loud,
   loutish, lumpish, massive, meretricious, oafish, obscene, opaque,
   out-and-out, outright, perfect, positive, precious, profound,
   pronounced, proper, rank, raw, regular, ribald, rough, rude,
   shattering, shocking, sottish, stark, stark-staring, stupid,
   superlative, surpassing, the veriest, thick, thick-bodied,
   thickset, thorough, thoroughgoing, three-dimensional, total,
   unbearable, unconscionable, uncouth, undeniable, unequivocal,
   unmitigated, unqualified, unrefined, unrelieved, unspoiled,
   unteachable, utter, viscous, vulgar, wrongheaded