Webster's Revised Unabridged Dictionary · 1913

Breastplate

Breastplate ({not transcribed}) , noun

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 Antiquities) 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.