Entry 1 sense Webster, 1913 Heretical /hẽr-ĕt'-ĭk-əl/ · He·ret·i·cal · IPA /həˈɹɛtɪkəl/ 01 a. Containing heresy; of the nature of, or characterized by, heresy. 1. Containing heresy; of the nature of, or characterized by, heresy.