The Collaborative International Dictionary of English v.0.48:

Corsage \Cor"sage\ (k[^o]r"s[asl]j), n. [F. See Corset.]
   1. The waist or bodice of a lady's dress; as, a low corsage.

   2. (k[^o]r*s[aum]zh") a flower or small arrangement of
      flowers worn by a person as a personal ornament. Typically
      worn by women on special occasions (as, at a ball or an
      anniversary celebration), a corsage may be worn pinned to
      the chest, or tied to the wrist. It is usually larger or
      more elaborate than a boutonniere.
      [PJC]

WordNet (r) 3.0 (2006):

corsage
    n 1: an arrangement of flowers that is usually given as a
         present [syn: bouquet, corsage, posy, nosegay]

Moby Thesaurus II by Grady Ward, 1.0:

20 Moby Thesaurus words for "corsage":
   blouse, bodice, boughpot, bouquet, boutonniere, buttonhole,
   chaplet, dickey, festoon, flower arrangement, garland, lei, linen,
   nosegay, posy, shift, shirt, spray, waist, wreath