Heretic, n.
Etymology: [L. haereticus, Gr. hérétique. See Heresy.]
1. One who holds to a heresy; one who believes some doctrine contrary to the established faith or prevailing religion. A man that is an heretic, after the first and second admonition, reject. Titus iii. 10.
2. (R. C. Ch.)
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." Addis & Arnold.
Syn. -- Heretic, Schismatic, Sectarian. A heretic is one whose errors are doctrinal, and usually of a malignant character, tending to subvert the true faith. A schismatic is one who creates a schism, or division in the church, on points of faith, discipline, practice, etc., usually for the sake of personal aggrandizement. A sectarian is one who originates or is an ardent adherent and advocate of a sect, or distinct organization, which separates from the main body of believers.
Shades of meaning
Etymologically, a heretic is one who takes or chooses his own belief, instead of the belief of his church; hence, a heretic is one who denies commonly accepted views, or who holds opinions contrary to the recognized standard or tenets of any established religious, philosophical, or other system, school, or party; the religious sense of the word is the predominant one; a schismatic is primarily one who produces a split or rent in the church. A heretic differs in doctrine from the religious body with which he is connected; a schismatic differs in doctrine or practise, or in both. A heretic may be reticent, or even silent; a schismatic introduces divisions. A heresiarch is the author of a heresy or the leader of a heretical party, and is thus at once a heretic and a schismatic. With advancing ideas of religious liberty, the odious sense once attached to these words is largely modified, and heretic is often used playfully. Dissenter and non-conformist are terms specifically applied to English subjects who hold themselves aloof from the Church of England; the former term is extended to non-adherents of the established church in some other countries, as Russia.