The Collaborative International Dictionary of English v.0.48:

Brassiere \Bras`siere"\ Brassiere
\Bras`si[`e]re"\(br[.a]*z[=e]r"), n. [F.]
   A form of woman's undergarment, often stiffened with wire or
   whalebones, or the like, and worn to cover and support the
   breasts; -- also called bra. It usually has straps which
   support it from the shoulders, but strapless variants are
   also made.

   Syn: bra, bandeau.
        [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

brassiere
    n 1: an undergarment worn by women to support their breasts
         [syn: brassiere, bra, bandeau]