Definition of "bruiser"

bruiser

noun
plural bruisers
1. (sports) In contact sports, an athlete whose size, strength, and/or aggressiveness make it likely that they will cause athletes on the opposing team to suffer physical punishment.
2. (by extension, colloquial, derogatory) A tall, strong, heavily built person, usually a man, especially one prone to physical violence; a strong and tough person.
  Quotations
  So there, my dear Bertie, was I, within a few hours of my entrance into this town, with my top-hat down to my ears, my highly professional frock-coat, and my kid gloves, fighting some low bruiser on a pedestal in one of the most public places, in the heart of a yelling and hostile mob! I ask you whether that was cruel luck or not?
  1895, A[rthur] Conan Doyle, chapter X, in The Stark Munro Letters: […], London: Longmans, Green, and Co.
3. A machine for bruising oats.
4. A person who enjoys arguing with others.
5. A professional boxer.
  Quotations
  Sometimes, when in the newspapers I happen upon descriptions of our modern bruisers and prizefighters, I wonder what chance the best of them would have had against him.
  1906–1907, Jack London, chapter V, in Before Adam