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.

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

Member of a branch of the Christian church that separated from the Roman Catholic church during the 16th century Reformation.

A group within the Christian faith that holds more liberal ideas than the traditional Roman Catholic Church.