interlanguage

noun

1. A language generated by a student of an additional language that incorporates aspects of their native language and the target language.“Trasyanka and Surzhyk are interlanguages: a Belarusian–Russian and a Ukrainian-Russian mixed language.”
2. A lingua franca, a common language used by speakers of different languages.“Latin used to be the European interlanguage. Currently English widely serves this purpose.”
3. A pidgin or creole.