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]