phylum definition
Full Definition of PHYLUM. 1. a: a direct line of descent within a group b: a group that constitutes or has the unity of a phylum; specifically: a primary category in biological taxonomy especially of animals that ranks above the class and below the kingdom â compare division 10.2.: a direct line of descent within a group b: a group that constitutes or has the unity of a phylum; specifically: a primary category in biological taxonomy especially of animals that ranks above the class and below the kingdom â compare division 10.