polyphyletic Syllabification: (pol·y·phy·let·ic)Pronunciation: /ˌpälifīˈletik/Definition of polyphyletic adjective Biology (of a group of organisms) derived from more than one common evolutionary ancestor or ancestral group and therefore not suitable for placing in the same taxon. polyphyletic in other Oxford dictionaries Definition of polyphyletic in the British & World English dictionary