A protruding stomach/pot belly, as a result of coming off heroin. Usually caused by overeating as a substitute for heroin. Can also be used to recognise weight gain as a result of coming of various other addictive substances.
Janey: "Wow, Brett's got a real heroin belly going on since he quick the smack."
Saffron: "I know, poor Brett, I wanna poke it."