ManichaeanPronunciation: /ˌmanɪˈkiːən/ (also Manichean)Definition of Manichaean adjective chiefly historical relating to Manichaeism. Philosophy relating to dualism; dualistic. noun an adherent of Manichaeism. Derivatives Manichaeanism noun Manichaean in other Oxford dictionaries Definition of Manichaean in the US English dictionary