1) Drinking heavily
2) Ordering drugs from a dealer
3) Obscure pseudonym for anal sex
Person 1: Dude, where's your dad?
Sonofadrunk: Playing chess.
Person 1: What were you doing in that back alley?
Druggie: Playing chess.
Person 1: What were you and that other guy doing in the locker room?
Gay dude: Playing chess... heehee!