exocytosis Syllabification: (ex·o·cy·to·sis)Pronunciation: /ˈeksōsīˈtōsis/Definition of exocytosis noun Biology a process by which the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane. Derivatives exocytoticPronunciation: /-ˈtätik/ adjective exocytosis in other Oxford dictionaries Definition of exocytosis in the British & World English dictionary