(n) a common language used by speakers of different languages, Syn. koine, interlanguage, Example:Koine is a dialect of ancient Greek that was the lingua franca of the empire of Alexander the Great and was widely spoken throughout the eastern Mediterranean area in Roman times
The Collaborative International Dictionary of English (GCIDE) v.0.53 Collaborative International Dictionary (GCIDE)
pos>n. [ It., prop., language of the Franks. ] 1. The commercial language of the Levant, -- a mixture of the languages of the people of the region and of foreign traders. [ 1913 Webster ]
2. Any hybrid or other language used over a wide area as a common or commercial tongue among peoples of different speech. [ Webster 1913 Suppl. ]