Apostate

1. To apostatize.
2. Pertaining to, or characterized by, apostasy; faithless to moral allegiance; renegade.
3. One who has forsaken the faith, principles, or party, to which he before adhered; esp., one who has forsaken his religion for another; a pervert; a renegade.
4. One who, after having received sacred orders, renounces his clerical profession.