Entry 1 sense Webster, 1913 Demonology · De·mon·ol·o·gy · IPA /ˌdiːməˈnɑːləd͡ʒi/ 01 n. A treatise on demons; a supposititious science which treats of demons and their manifestations. 1. A treatise on demons; a supposititious science which treats of demons and their manifestations.