Joint Body means in slang: The term “Joint Body” was a common expression used by law enforcement officers, particularly those who work undercover to find and eliminate ex-convicts and other felons. This refers to how an ex-*** behaves when in “joint.” The ex-***’s physique is enhanced by a confident, strut-like exterior walk. This refers to how much lean muscle an ex-*** gains while working in the “joint,” lifting weights. (in Slang Dictionary, added by Cupuliferous)