Fusion languages? Don't know what to call it?

An informal fusion without well defined rules of structure, grammar, etc. would be a pidgin. Pidgins can develop into creoles - more fully developed languages. If it's a mother tongue (ie, the chief language of a culture), it's likely a creole language. Creoles, however, don't necessarily have to develop from two seperate languages, but can develop from one "mother" language, while pidgin is usually a blend of two or more.