lysosome Syllabification: (ly·so·some)Pronunciation: /ˈlīsəˌsōm/Definition of lysosome noun Biology an organelle in the cytoplasm of eukaryotic cells containing degradative enzymes enclosed in a membrane. Derivatives lysosomalPronunciation: /ˌlīsəˈsōməl/ adjective lysosome in other Oxford dictionaries Definition of lysosome in the British & World English dictionary