Abbott-Smith Manual Greek Lexicon
ἀκρο-γωνιαῖος (G204)
2 † ἀκρο-γωνιαῖος , -αία, -αῖον ( ἄκροι , γωνία , an angle ) [in LXX: Is 28:16 ( פִּנָּה )*;] = Attic γωνιαῖος (freq. in Inscr.; MM, VGT , s.v. ἀ. ), at the extreme angle : ὁ ἀ. , the corner foundation stone , Eph 2:20 , I Pe 2:6 .†
G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922) — public domain