Heretic

Webster's Dictionary

(1): ( n.) One who holds to a heresy; one who believes some doctrine contrary to the established faith or prevailing religion.

(2): ( n.) One who having made a profession of Christian belief, deliberately and pertinaciously refuses to believe one or more of the articles of faith "determined by the authority of the universal church."

Charles Buck Theological Dictionary

A general name for all such persons under any religion, but especially the Christian, as profess or teach opinions contrary to the established faith, or to what is made the standard of orthodoxy.

See last article, and Lardner's History of the Heretics of the first two Centuries.