A baseball slang term referring to the modification of a baseball bat by inserting cork or another light substance to make the bat lighter, and thus easier to swing, without losing too much power.
In Major League Baseball it is illegal for a baseball bat to be modified in such a way that gives a possibly unfair advantage to a batter. A traditional corked bat is created by drilling a core in the thick end of the bat and inserting cork into the newly created gap. The end of the bat is then sealed up. In all, only six major league players have been penalized for using corked bats, the most recent being Sammy Sosa in 2003. The assumed advantage of using a corked bat has since been proven scientifically ineffective as the physics do not give the collision any additional elasticity.