1. The jargon, slang, specialized vocabulary, or set of idioms used by a particular group.
2. The jargon of thieves or vagabonds, intended to conceal meaning from outsiders.
Etymology: French, but the details of the word's origin are unclear. It seems the word originally referred to a group of thieves (les argotiers) rather than their jargon.
"Argot is nothing more nor less than a wardrobe in which language, having some bad deed to do, disguises itself. It puts on word-masks and metaphoric rags."
- Victor Hugo, "Les Miserables"