Boyd’s Bible Dictionary:
The breastplate of the high priest (Ex. 28:15), was of embroidered stuff, some 10 inches square; its upper corners fastened with gold or lace to the ephod, its lower to the girdle (Ex. 28:28). Adorned with 12 precious stones (Ex. 28:12-29).
Concise Bible Dictionary:
Armor for the breast.
1. Of righteousness (for Christ) (Isa. 59:17); (for the Christian’s conflict in the heavenlies) (Eph. 6:14).
2. Of faith and love (for the wilderness) (1 Thess. 5:8).
3. Of iron (steeled conscience) (Rev. 9:9).
4. Of fire, jacinth, and brimstone (dire judgments) (Rev. 9:17). See ARMOR.
Medieval Breastplates
Strong’s Dictionary of Greek Words:
Meaning:
of uncertain affinity; the chest ("thorax"), i.e. (by implication) a corslet