To abandon or renounce one's religion, political allegiance, or core principles.
From 'apostacy' with the verb-forming suffix '-ize'. This variant spelling (more common in older texts) means the same as 'apostatize' but follows a different English spelling convention.
Medieval churches kept lists of people who apostacized—and it was dangerous because apostasy could mean execution, so those who did it were making a life-or-death choice about what they believed in.
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