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.
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.
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