endospore Syllabification: (en·do·spore)Pronunciation: /ˈendəˌspôr/Definition of endospore noun Biology a resistant asexual spore that develops inside some bacteria cells. the inner layer of the membrane or wall of some spores and pollen grains. Derivatives endosporousPronunciation: /enˈdäspərəs, ˌendəˈspôrəs/ adjective endospore in other Oxford dictionaries Definition of endospore in the British & World English dictionary