Source : Webster's Revised Unabridged Dictionary (1913)

Breastplate \Breast"plate`\, n.
   1. A plate of metal covering the breast as defensive armor.

            Before his old rusty breastplate could be scoured,
            and his cracked headpiece mended.     --Swift.

   2. A piece against which the workman presses his breast in
      operating a breast drill, or other similar tool.

   3. A strap that runs across a horse's breast. --Ash.

   4. (Jewish Antiq.) A part of the vestment of the high priest,
      worn upon the front of the ephod. It was a double piece of
      richly embroidered stuff, a span square, set with twelve
      precious stones, on which were engraved the names of the
      twelve tribes of Israel. See {Ephod}.

Source : WordNet®

breastplate
     n : armor plate that protects the chest; the front part of a
         cuirass [syn: {aegis}, {egis}]