apostasy
formal disaffiliation from or abandonment or renunciation of a religion
apostasy in Islam
repudiation of Islam
apostasy in Christianity
repudiation of the Christian faith
Apostasy in Judaism
rejection of Judaism and possible conversion to another religion
ex-Mormon
disaffiliate of The Church of Jesus Christ of Latter-day Saints
Covenant-breaker
term refering to a person who has been excommunicated from the Baháʼí community for the act of covenant-breaking