The Collaborative International Dictionary of English v.0.48:

Coarse \Coarse\ (k[=o]rs), a. [Compar. Coarser
   (k[=o]rs"[~e]r); superl. Coarsest.] [As this word was
   anciently written course, or cours, it may be an abbreviation
   of of course, in the common manner of proceeding, common, and
   hence, homely, made for common domestic use, plain, rude,
   rough, gross, e. g., "Though the threads be course."
   --Gascoigne. See Course.]
   [1913 Webster]
   1. Large in bulk, or composed of large parts or particles; of
      inferior quality or appearance; not fine in material or
      close in texture; gross; thick; rough; -- opposed to
      fine; as, coarse sand; coarse thread; coarse cloth;
      coarse bread.
      [1913 Webster]

   2. Not refined; rough; rude; unpolished; gross; indelicate;
      as, coarse manners; coarse language.
      [1913 Webster]

            I feel
            Of what coarse metal ye are molded.   --Shak.
      [1913 Webster]

            To copy, in my coarse English, his beautiful
            expressions.                          --Dryden.

   Syn: Large; thick; rough; gross; blunt; uncouth; unpolished;
        inelegant; indelicate; vulgar.
        [1913 Webster]

WordNet (r) 3.0 (2006):

coarse
    adj 1: of textures that are rough to the touch or substances
           consisting of relatively large particles; "coarse meal";
           "coarse sand"; "a coarse weave" [syn: coarse, harsh]
           [ant: fine]
    2: lacking refinement or cultivation or taste; "he had coarse
       manners but a first-rate mind"; "behavior that branded him as
       common"; "an untutored and uncouth human being"; "an uncouth
       soldier--a real tough guy"; "appealing to the vulgar taste
       for violence"; "the vulgar display of the newly rich" [syn:
       coarse, common, rough-cut, uncouth, vulgar]
    3: of low or inferior quality or value; "of what coarse metal ye
       are molded"- Shakespeare; "produced...the common cloths used
       by the poorer population" [syn: coarse, common]

Moby Thesaurus II by Grady Ward, 1.0:

268 Moby Thesaurus words for "coarse":
   Adamic, Circean, Doric, Mickey Mouse, acerb, acerbic, acrid,
   amaroidal, animal, animalistic, arrested, astringent, backward,
   barbaric, barbarous, base, bawdy, beastlike, beastly, bestial,
   bitter, bitter as gall, blustering, blustery, bodily, boorish,
   brassy, brazen, bristly, broad, broad-bodied, broken, brutal,
   brute, brutish, bulky, bullnecked, bumpy, cacophonous, caddish,
   caked, cakey, carnal, carnal-minded, caustic, cheap, cheesy,
   choked, choppy, clumsy, coarse-grained, common, corpulent,
   corrugated, cracked, crass, croaking, croaky, cross-grained, crude,
   dense, dirty, doggerel, dry, dysphemistic, earthy, embryonic,
   fallen, fat, filthy, fleshly, foul, foul-mouthed, fourth-class,
   frank, full, full-bodied, furious, gaudy, graceless, grained,
   grainy, granular, granulated, gritty, gross, gruff, gutter,
   guttural, hard, harsh, harsh-sounding, heavy, heavyset, hoarse,
   homespun, horripilant, husky, ill-bred, ill-mannered, impolite,
   improper, impure, in bad taste, in embryo, in ovo, in the rough,
   inconcinnate, inconcinnous, inconsiderate, incorrect, indecent,
   indecorous, indelicate, inelegant, inequal, inexpert, infelicitous,
   inferior, insensitive, irregular, jolty, kitschy, lapsed,
   lascivious, lewd, linsey-woolsey, loud, loutish, louty, low,
   low-class, low-grade, low-quality, low-test, lumpy, massive,
   material, materialistic, mean, meretricious, metallic, nasty,
   nonspiritual, obscene, offensive, orgiastic, outlandish,
   oversimple, paltry, physical, pimply, pitted, pocky, poor,
   postlapsarian, potholed, prentice, prickly, pungent, punk, raffish,
   ragged, raging, rank, raucid, raucous, raunchy, raw,
   reductionistic, reductive, ribald, ripply, rough, rough-cast,
   rough-grained, rough-hewn, roughcast, roughhewn, roughneck, roupy,
   rowdy, rude, rudimental, rudimentary, ruffled, rutted, rutty,
   scatological, scratchy, second-best, second-class, second-rate,
   seedy, shabby, shagged, shaggy, sharp, shoddy, simplistic, smutty,
   sour, squawking, squawky, stertorous, stormy, strangled, stunted,
   swinish, tacky, tactless, tart, tasteless, tawdry, tempestuous,
   textured, thick, thick-bodied, thickset, third-class, third-rate,
   three-dimensional, throaty, tinny, trashy, turbulent, unblown,
   uncivil, uncourtly, uncouth, uncultivated, uncultured, uncut,
   underdeveloped, undeveloped, undignified, uneuphonious, uneven,
   unfashioned, unfelicitous, unfeminine, unfinished, unformed,
   ungenteel, ungentle, ungentlemanly, ungraceful, unhewn, unkempt,
   unlabored, unladylike, unlevel, unlicked, unpolished, unprocessed,
   unrefined, unseemly, unsmooth, unsolicitous, unspiritual,
   untreated, ununiform, unworked, unwrought, viscous, vulgar,
   vulgarian, wimpled