Someone who exists on several worlds at the same time, as in a stock broker by day and a punk by night or a hi-tech big wig and a DJ. Usually with aptitude in one or both areas.
"That Eddie, a bridge runner, i tell you. Saw him last night bartending my local bar. Look at him now doing the accounting."
"She's a bridge runner. Saw her giving head behind the dumpster at that club last night, she was so hot, now she wants to fire me?