Source : Webster's Revised Unabridged Dictionary (1913)

Brassiere \Bras`si[`e]re"\, n. [F.]
   A form of woman's underwaist stiffened with whalebones, or
   the like, and worn to support the breasts.

Source : WordNet®

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