n. 1. A plate of metal covering the breast as defensive armor. [ 1913 Webster ] Before his old rusty breastplate could be scoured, and his cracked headpiece mended. Swift. [ 1913 Webster ] 2. A piece against which the workman presses his breast in operating a breast drill, or other similar tool. [ 1913 Webster ] 3. A strap that runs across a horse's breast. Ash. [ 1913 Webster ] 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. [ 1913 Webster ] | 
