evolutionist Syllabification: (ev·o·lu·tion·ist)Pronunciation: /ˌevəˈlo͞oSHənist/Definition of evolutionist noun a person who believes in the theories of evolution and natural selection. adjective of or relating to the theories of evolution and natural selection:an evolutionist modelDerivatives evolutionismPronunciation: /-ˌnizəm/ noun evolutionist in other Oxford dictionaries Definition of evolutionist in the British & World English dictionary