apostasy

noun

1. (countable, uncountable)The renunciation of a belief or set of beliefs.

   “The apparition of Lawyer Clippurse at the Hall occasioned much speculation in that portion of the world to which Waverley-Honour formed the centre: but the more judicious politicians of this microcosm augured yet worse consequences to Richard Waverley from a movement which shortly followed his apostasy.”

   “The King of Navarre suddenly abandoned his party and went over to the Catholics. The explanation of his apostasy was as simple as it was base: Navarre had no confidence in the success of his cause, and he cared little in his heart for anything but women and vanity.”

   “What had he said, what had he done, after all, to give them the right to fasten on him the charge of apostasy? He had always been a free critic of everything, and it was natural that, on certain occasions, in the little parlour in Lisson Grove, he should have spoken in accordance with that freedom; but it was only with the Princess that he had permitted himself really to rail at the democracy and given the full measure of his scepticism.”

2. (countable, uncountable)Specifically, the renunciation of one's religion or faith.