A-pŏs'ta-sy, n.

n. [Lat. apostasia, Gr. ἀποστασία, a standing off from, a defection, from ἀποστῆναι, to stand off, to revolt, from ἀπό, from, and στῆναι, to stand.] An abandonment of what one has voluntarily professed; a total desertion or departure from one's faith, principles, or party.