Argot

(n.) A secret language or conventional slang peculiar to thieves, tramps, and vagabonds; flash.

Thesaurus Entries

Aesopian language, Babel, Greek, babble, cant, cipher, code, cryptogram, double Dutch, garble, gibberish, gift of tongues, glossolalia, gobbledygook, jargon, jumble, lingo, mumbo jumbo, noise, patois, patter, phraseology, scatology, scramble, secret language, slang, taboo language, vernacular, vocabulary, vulgar language