phagosome Syllabification: (phag·o·some)Pronunciation: /ˈfagəˌsōm/Definition of phagosome noun Biology a vacuole in the cytoplasm of a cell, containing a phagocytosed particle enclosed within a part of the cell membrane. Derivatives phagosomalPronunciation: /ˌfagəˈsōməl/ adjective phagosome in other Oxford dictionaries Definition of phagosome in the British & World English dictionary