The Collaborative International Dictionary of English v.0.48:

cabochon \ca`bo`chon"\ (k[a^]`b[u^]*sh[aum]n"; Fr.
   k[.a]`b[-o]`sh[^o]N"), n. [F.] (Jewelry)
   A stone of convex form, highly polished, but not faceted;
   also, the style of cutting itself. Such stones are said to be
   cut en cabochon.
   [Webster 1913 Suppl. +PJC]

The Collaborative International Dictionary of English v.0.48:

cabochon \ca`bo`chon"\ (k[a^]`b[u^]*sh[aum]n"; Fr.
   k[.a]`b[-o]`sh[^o]N"), a. [see cabochon, n..] (Jewelry)
   Of, pertaining to, containing, or in the style of, a
   cabochon.
   [PJC]

WordNet (r) 3.0 (2006):

cabochon
    n 1: a highly polished gem that is cut convexly but without
         facets