1. Someone who has been in the scene before you or your group.
2. Someone who is still in the scene beyond the 'acceptable' or expected age.
Often form cliques of their own and try and school youngin's on how things used to be back in their day. A scene-specific 'senior citizen,' for all intents and purposes, in activities that would kill normal seniors citizens (drug/club/rave scene).
Dude, I just bought some weed off of some 40 something down on the dance floor!
Yeah I know that guy, he's an old head.