In contact sports, an athlete whose size, strength, and/or aggressiveness make it likely that he will cause athletes on the opposing team to suffer physical punishment.
(by extension) a tall, strong, heavily built man, especially one prone to physical violence; a thug.
His "assistant" was a big bruiser named Pete, who, with his enormous shoulders and menacing scowl, was clearly present for the intimidation factor.
A machine for bruising oats.