The Collaborative International Dictionary of English v.0.48:
Argot \Ar`got"\, n. [F. Of unknown origin.] A secret language or conventional slang peculiar to thieves, tramps, and vagabonds; flash. [1913 Webster]WordNet (r) 3.0 (2006):
argot n 1: a characteristic language of a particular group (as among thieves); "they don't speak our lingo" [syn: slang, cant, jargon, lingo, argot, patois, vernacular]