Definition of "pusherman"

Well, now if I were the president of this land / You know, I'd declare total war on the pusher man

1968, Hoyt Axton (lyrics and music), “The Pusher”, in Steppenwolf, performed by Steppenwolf

The visitors stepped back, identical expressions of frustration and distress on their faces — they looked like hurting junkies who had discovered the pusherman wasn't where he'd promised to be.

1991, Stephen King, Needful Things