θυρεός, -οῦ, ὁ (< θύρα), [in LXX for מָגֵן, צִנָּה ;] __1. in Hom., a door-stone. __2. In late Gk. (Polyb., Plut.), the scutum, a large oblong shield: θ. τ. πίστεως, Eph.6:16 (cf. Wis.5:20, where ὁσιότης is likened to the ἀσπίς, the clypeus or small round shield of the light-armed soldier).† (AS)
Thayer:
1) a shield, a large oblong, four cornered shield
θυρεός
thureos
thoo-reh-os'
From G2374; a large shield (as door shaped)