bac ‧ te ‧ ri ‧ a /bækˈtɪəriə $ -ˈtɪr-/ BrE AmE noun [plural] ( singular bacterium /-riəm/)
[ Date: 1800-1900 ; Language: Modern Latin ; Origin: Greek bakterion 'stick, rod' ; because of their shape ]
very small living things, some of which cause illness or disease ⇨ virus
—bacterial adjective :
a bacterial infection