(n.) One who forsakes a duty, a cause or a party, a friend, or any one to whom he owes service; especially, a soldier or a seaman who abandons the service without leave; one guilty of desertion.

Sabbath-breaker absconder apostasy apostate atheist backslider betrayal blasphemer bolt bolter breakaway collaborationist collaborator convert defection defector dereliction desertion escapee fifth columnist fugitive mugwump outlaw proselyte quisling rat ratting recidivist recreant renegade renegado renegate reversionist runagate runaway sacrilegist schism schismatic seceder secession secessionist separatist strikebreaker tergiversant tergiversator traitor turnabout turncoat turntail unbeliever walkout