Boxer

noun

1. A participant (fighter) in a boxing match.

   "You can tell she's a boxer by looking at her nose."

2. A breed of stocky, medium-sized, short-haired dog with a square-jawed muzzle.
3. A type of internal combustion engine in which cylinders are arranged in two banks on either side of a single crankshaft.
4. The person running a game of two-up.
5. One who packs boxes.