endocarditisPronunciation: /ˌɛndəʊkɑːˈdʌɪtɪs/Definition of endocarditis noun [mass noun] Medicine inflammation of the endocardium. Derivatives endocarditicPronunciation: /-ˈdɪtɪk/ adjective endocarditis in other Oxford dictionaries Definition of endocarditis in the US English dictionary