A person who starts doing drugs and joins a group of people who are heavily into that drug(s) already. Then after a short while, leaves the group because they can't keep up with the group's high level of partying.
Joe - Hey Keith, who's that kid who was at your apartment last night in the corner tweaking out?
Keith - Oh, thats just some interlooper we met the other day. He won't last long partying with us.
Joe - I hope he doesn't od
trying to keep up with us.