A common language used by speakers of different languages WordNet 3.0 & Open English WordNet

A lingua franca, also known as a bridge language, common language, trade language, auxiliary language, vehicular language, or link language, is a language systematically used to make communication possible between groups of people who do not share a native language or dialect, particularly when it is a third language that is distinct from both of the speakers' native languages. Wikipedia

An interlanguage is an idiolect which has been developed by a learner of a second language which preserves some features of their first language and can overgeneralize some L2 writing and speaking rules. Wikipedia

Language used for communication between speakers of different languages. Wikipedia Disambiguation

An idiolect that has been developed by a learner of a second language Wikipedia Disambiguation

Emerging language system in the mind of a second language learner. Wikipedia Disambiguation

Languages used to facilitate trade between groups without a common native language Wikidata

Idiolect used by a second language learner Wikidata

A common language used by speakers of different languages. OmegaWiki

An extinct language of Tunisia. OmegaWiki

A lingua franca, a common language used by speakers of different languages. Wiktionary

A common language used by people of diverse backgrounds to communicate with one another, often a basic form of speech with simplified grammar, particularly, one not the first language of any of its speakers. Wiktionary

Common language. Wiktionary (translation)