come-outer

Etymology
, referring to a passage in Corinthians in the Bible: "come out from among them, and be ye separate".

Noun

 * 1) One who abandons or withdraws from an established religion, opinion, custom, creed, etc.
 * Despite her family's wishes, she left Christianity, becoming a come-outer of her former faith.
 * 1) One who seeks radical political or religious reform.