'Breastplate' definitions:

Definition of 'breastplate'

noun

Armor plate that protects the chest; the front part of a cuirass [syn: breastplate, aegis, egis]

From: GCIDE

Breastplate \Breast"plate`\, 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] Breastplow

Breastplate
That piece of ancient armour that protected the breast. This word is used figuratively in Eph. 6:14 and Isa. 59:17. (See ARMOUR.)
An ornament covering the breast of the high priest, first mentioned in Ex. 25:7. It was made of embroidered cloth, set with four rows of precious stones, three in each row. On each stone was engraved the name of one of the twelve tribes (Ex. 28:15-29; 39:8-21). It was in size about ten inches square. The two upper corners were fastened to the ephod by blue ribbons. It was not to be "loosed from the ephod" (Ex. 28:28). The lower corners were fastened to the girdle of the priest. As it reminded the priest of his representative character, it was called the memorial (28:29). It was also called the breastplate of judgment (28:15). (See PRIEST.)