Dictionary: Easton's Bible Dictionary
used in defensive warfare, varying at different times and under different circumstances in size, form, and material (1 Sam. 17:7; 2 Sam. 1:21; 1 Kings 10:17; 1 Chr. 12:8, 24, 34; Isa. 22:6; Ezek. 39:9; Nahum 2:3).
Used figuratively of God and of earthly princes as the defenders of their people (Gen. 15:1; Deut. 33:29; Ps. 33:20; 84:11). Faith is compared to a shield (Eph. 6:16).
Shields were usually "anointed" (Isa. 21:5), in order to preserve them, and at the same time make the missiles of the enemy glide off them more easily.