Fanatic

Part of speech: noun (n.)

A person affected by excessive enthusiasm, particularly on religious subjects; one who indulges wild and extravagant notions of religion. There is a new word, coined within few months, called fanatics, which, by the close stickling thereof, seemeth well cut out and proportioned to signify what is meant thereby, even the sectaries of our age. Fuller (1660). Fanatics are governed rather by imagination than by judgment. Stowe.

Part of speech: adjective (a.)

Pertaining to, or indicating, fanaticism; extravagant in opinions; ultra; unreasonable; excessively enthusiastic, especially on religious subjects; as, fanatic zeal; fanatic notions. But Faith, fanatic Faith, once wedded fast To some dear falsehood, hugs it to the last. T. Moore.