noun.
An abandonment of what one has professed; a total desertion of, or departure from, one's faith, principles, or party.
noun.
In theology, a total abandonment of the Christian faith.
noun.
In Rom. Cath. eccles. law: A persistent rejection of ecclesiastical authority by a member of the church. An abandonment without permission of the religious order of which one is a member. A renunciation of the clerical profession by one who has received major orders.
noun.
In medicine, same as apostasis.
noun.
Also spelled apostacy.