Extended Strong's Greek Lexicon (Abbott-Smith based)
cornerstone
Usage: ἀκρο-γωνιαῖος, -αία, -αῖον (ἄκροι, γωνία, an angle) [in LXX: Isa.28:16 (פִּנָּה) * ;] = Attic γωνιαῖος (frequently in Inscr.; MM, VGT, see word ἀ.), at the extreme angle: ὁ ἀ., the corner foundation stone, Eph.2:20, 1Pe.2:6.† (AS)