1. (n.) A member of the Western Christian church with doctrine founded on the principles of the Reformation\; one who protests; -- originally applied to those who adhered to Luther, and protested against, or made a solemn declaration of dissent from, a decree of the Emperor Charles V. and the Diet of Spires, in 1529, against the Reformers, and appealed to a general council; -- now used in a popular sense to designate any Christian who does not belong to the Roman Catholic or the Greek Church.

2. (a.) Making a protest; protesting.

3. (a.) of or pertaining to the faith and practice of those Christians who reject the authority of the Roman Catholic Church; as, Protestant writers.

Sabbath-breaker atheist atheistic backslider backsliding blasphemer blasphemous bolter collaborationist collaborative collaborator convert defector degenerate demurrer deserter disloyal dissenter dissentient dissident faithless fallen fallen from grace fifth columnist impious irreligious irreverent lapsed mugwump nonconformist objector opinionist opposition voice profanatory profane proselyte protestant protester quisling rat recidivist recidivistic recreant recusant renegade renegado renegate reversionist runagate sacrilegious sacrilegist schismatic seceder secessionist sectarian sectary separatist strikebreaker tergiversant tergiversating tergiversator traitor traitorous treasonable treasonous turnabout turncoat turntail unbeliever undutiful