Hĕr'e-si-ārch or He-rē'si-ārch, n.

(Synop., §130), n. [Gr. αἱρεσιάρχης, αἱρεσίαρχος, from αἵρεσις, heresy, and ἀρχός, leader, ἄρχειν, to lead; Lat. hæresiarcha, Fr. hérésiarque, Pr., Sp., & Pg. heresiarca, It. eresiarca.] A leader in heresy; the chief of a sect of heretics. Stillingfleet.