heretic /ˈhɛɹɪtɪk/noun 2adjective 1forms 3 noun2 •Someone whose beliefs are contrary to the fundamental tenets of a religion they claim to belong to.He semeth a sysmatyke Or els an heretike, For fayth in hym is faynte. — 1503 •Someone who does not conform to generally accepted beliefs or practices. adjective1 •(no longer used) Heretical; of or pertaining to heresy or heretics. formsheretics · more heretic · most heretic