A mother tongue that originates from contact between two languages WordNet 3.0 & Open English WordNet

A creole language, or simply creole, is a stable natural language that develops from the process of different languages simplifying and mixing into a new form, and then that form expanding and elaborating into a full-fledged language with native speakers, all within a fairly brief period of time. Wikipedia

A language that originated as a mixed language. Many creole languages are known by their speakers as some variant of "creole", for example spelled Kriol. Wikipedia Disambiguation

Stable natural languages that have developed from a pidgin Wikidata

A stable language that originates seemingly as a "new" language, sometimes with features that are not inherited from any apparent source, without however qualifying in any appreciable way as a mixed language. OmegaWiki

A lect formed from two or more languages which has developed from a pidgin to become a first language. Wiktionary

Lect formed from two languages. Wiktionary (translation)