D defs.my
Entry 3 senses Webster, 1913

Pusher

/po͝osh'-ẽr/ · Push·er · IPA /ˈpʊʃə/
01 n. One who, or that which, pushes.
  1. 1.
    One who, or that which, pushes.
  2. 2.
    One who sells illegal drugs, esp. one who tries to convince others to use such drugs.
  3. 3.
    a second engine attached to the rear of a train to provide extra power for climbing steep grades.(Railroad)