ἀκρόγωνος

From LSJ

θοῦ, Κύριε, φυλακὴν τῷ στόµατί µου καὶ θύραν περιοχῆς περὶ τὰ χείλη µου → set a guard over my mouth, Lord; keep watch over the door of my lips | set a guard, O Lord, over my mouth; keep watch over the door of my lips (Psalm 140:3, Septuagint version)

Source

Spanish (DGE)

-ον
angular
1 fig. piedra angular (sc. λίθος) de Cristo Σωτῆρα τὸν ἀκρόγωνον ἐκμιμούμενος Gr.Naz.M.37.1246A.
2 subst. τὸ ἀ. ángulo extremo, límite extremo τῆς ἐπαύλεως PMasp.109.26, cf. 151.113 (ambos VI d.C.).