mafiosoEnglishOxford Dictionary of Englishmafioso /ˌmafiˈəʊzəʊ / ▸ noun (plural mafiosi /ˌmafɪˈəʊzi, ˌmafɪˈəʊsi/) a member of the Mafia or a similar criminal organization: police received information from a former mafioso who became an informer. – ORIGIN Italian.