diplococcusPronunciation: /ˌdɪplə(ʊ)ˈkɒkəs/Definition of diplococcus noun (plural diplococci /-k(s)ʌɪ, -k(s)iː/) a bacterium that occurs as pairs of cocci, e.g. pneumococcus. diplococcus in other Oxford dictionaries Definition of diplococcus in the US English dictionary