unconvert

From un- +‎ convert.

unconvert (third-person singular simple present unconverts, present participle unconverting, simple past and past participle unconverted)

1. (transitive) To reverse the conversion of.
2. (intransitive) To deconvert; to undergo a deconversion from a religion, faith or belief.
   • 2015 November 10, Radhika Sanghani, quoting Hannah Martin, “Zooey Deschanel is Jewish. These three women changed their religions for love too”, in The Telegraph‎:

     I never ‘unconverted’ from Islam because I didn’t feel it was a significant thing for me. In my mind there’s no god - that’s why I was able to convert and not feel the need to officially revert.