c.1300, "embodiment of God in the person of Christ," from Old French incarnacion (12c.), from Late Latin incarnationem (nominative incarnatio), "act of being made flesh" (used by Church writers especially of God in Christ), noun of action from past participle stem of Latin incarnare "to make flesh," from in- "in" (see in- (2)) + caro (genitive carnis) "flesh" (see carnage).
that act of grace whereby Christ took our human nature into union with his Divine Person, became man. Christ is both God and man. Human attributes and actions are predicated of him, and he of whom they are predicated is God. A Divine Person was united to a human nature (Acts 20:28; Rom. 8:32; 1 Cor. 2:8; Heb. 2:11-14; 1 Tim. 3:16; Gal. 4:4, etc.). The union is hypostatical, i.e., is personal; the two natures are not mixed or confounded, and it is perpetual.