The private vocabulary and idiom of a particular group, often occupational, criminal, or subcultural. It is used to signal belonging, conceal meaning, or sharpen experience into insider terms. Where jargon can be merely technical, argot has the tang of the unofficial and the in-group.

Borrowed from French argot, originally applied to the speech of thieves and beggars and later generalized. Its ultimate origin is uncertain, which suits the word: a term for language that keeps its sources deliberately obscure.