A slang term in baseball referring to a pitcher who is known for attempting to hit batters in the head.
A "headhunter" is a term most often applied to pitchers who commonly throw pitches known as "beanballs." The "bean" is a slang term used to represent the batter's head. While many pitchers will throw a "brushback pitch" to attempt to get a batter who is crowding the plate to back off, a headhunter specifically throws a pitch with the intention of hitting the batter. This is usually the result of a pitcher being angered at the current batter, either directly (e.g. the pitcher gave up a home run in a previous at-bat to the same hitter) or indirectly. Such a reputation will often give an advantage to the pitcher, as batters may approach their at-bats differently. Beanball pitches will often result in the batter charging the mound and a subsequent bench-clearing brawl.