Source : Webster's Revised Unabridged Dictionary (1913)

Stomacher \Stom"ach*er\, n.
   1. One who stomachs.

   2. (? or ?) An ornamental covering for the breast, worn
      originally both by men and women. Those worn by women were
      often richly decorated.

            A stately lady in a diamond stomacher. --Johnson.

Source : WordNet®

stomacher
     n : garment consisting of a V-shaped panel of stiff material
         worn over the chest and stomach in the 16th century