Entry 1 sense Webster, 1913 Bacteriology /băkˌ-tĭr-ēˌ-äl'-əj-ē/ · Bac·te·ri·ol·o·gy · IPA /bækˌtɪəɹ.ɪˈɒləd͡ʒi/ 01 n. The branch of microbiology relating to bacteria. 1. The branch of microbiology relating to bacteria.(Biol.)