This is a term used in baseball to describe a specific type of intentional ball. In this particular case, the pitcher throws the ball harder to allow the catcher more time to throw out a runner trying to steal a base or to prevent a hit and run. The ball is ideally thrown to a position far outside the plate and high enough so the catcher may easily jump up, catch the ball, and make the necessary throw without interference from the batter. If a steal is not attempted, the pitchout will also serve as a good preventative measure.
A pitchout would be called by the manager who believes a base runner intends to steal, but is may also be called by the catcher, who has an excellent view of the lead the runner on first or second may be taking. It a runner does in fact attempt a steal on a pitchout, they have very little chance of success if the pitch is thrown accurately. A good pitchout also prevent the offensive team from employing the hit and run by removing ability of the batter to hit the ball. This will force the runner to either attempt a steal or stay on their current base.