Apostate
From XFamily - Children of God
Definition
a·pos·tate (ə-pŏs'tāt', -tĭt) n.
One who has abandoned one's religious faith, a political party, one's principles, or a cause. A person who has defected.
Middle English, from Old French, from Late Latin apostata, from Greek apostates, from aphistanai, to revolt.
