apostate apostate /əˈpɔsteɪt/

adjective

1. Not faithful to religion, party or cause  ( apostate )
   not faithful to religion, party or cause
   

noun

1. A disloyal person who betrays or deserts his cause or religion or political party or friend etc.  ( apostate , deserter , ratter , recreant [Archaic] , renegade , turncoat )
   a disloyal person who betrays or deserts his cause or religion or political party or friend etc.