Fleming, Sir Al ‧ ex ‧ an ‧ der /ˌælɪɡˈzɑːndəʳ $ -ˈzæn-/ BrE AmE
(1881–1955) a British scientist who discovered ↑ penicillin , a substance that is used as a medicine to destroy ↑ bacteria (=very small living things related to plants, some of which cause disease)