Slang

A slang is a vocabulary (words, phrases, and linguistic usages) of an informal register, common in everyday conversation but avoided in formal writing and speech. It also often refers to the language exclusively used by the members of particular in-groups in order to establish group identity, exclude outsiders, or both. The word itself came about in the 18th century and has been defined in multiple ways since its conception, with no single technical usage in linguistics. Provided by Wikipedia