endocytosis Syllabification: (en·do·cy·to·sis)Pronunciation: /ˌendōsīˈtōsis/Definition of endocytosis noun Biology the taking in of matter by a living cell by invagination of its membrane to form a vacuole. Derivatives endocytosePronunciation: /ˌendōsīˈtōs, -ˈtōz/ verb endocytoticPronunciation: /-ˈtätik/ adjective endocytosis in other Oxford dictionaries Definition of endocytosis in the British & World English dictionary