Source : Webster's Revised Unabridged Dictionary (1913)

Argot \Ar`got"\, n. [F. Of unknown origin.]
   A secret language or conventional slang peculiar to thieves,
   tramps, and vagabonds; flash.

Source : WordNet®

argot
     n : a characteristic language of a particular group (as among
         thieves); "they don't speak our lingo" [syn: {cant}, {jargon},
          {slang}, {lingo}, {patois}, {vernacular}]