From Longman Dictionary of Contemporary Englishlingua francalin‧gua fran‧ca /ˌlɪŋɡwə ˈfræŋkə/ noun [countable usually singular] SLa language used between people whose main languages are different English is the lingua franca in many countries.
Examples from the Corpus
lingua franca• Photographic reportage, the cinema and television have produced a lingua franca of universally comprehensible pictures.• And in a country whose language has become the world's lingua franca its literary culture is its culture.• Swahili is the lingua franca of East Africa.Origin lingua franca (1600-1700) Italian “tongue of the Franks” 