A quick pitch in baseball

Baseball

Baseball is a bat-and-ball sport played between two teams of nine players each. The aim is to score runs by hitting a thrown ball with a bat and touching a series of four bases arranged at the corners of a ninety-foot diamond...

 occurs when the pitcher throws a pitch

Pitch (baseball)

In baseball, a pitch is the act of throwing a baseball toward home plate to start a play. The term comes from the Knickerbocker Rules. Originally, the ball had to be literally "pitched" underhand, as with pitching horseshoes. Overhand throwing was not allowed until 1884.The biomechanics of...

 to home plate before the batter has had a chance to fully ready himself. It is illegal in all forms of baseball, and it has various penalties, depending on the situation: if there is no runner on base, the pitch is called a ball, but if there are any number of runners, it is ruled a balk

Balk

In baseball, a pitcher can commit a number of illegal motions or actions that constitute a balk. In games played under the Official Baseball Rules, a balk results in a dead ball or delayed dead ball. In certain other circumstances, a balk may be wholly or partially disregarded...

. For a pitch to be ruled a quick pitch, it is necessary for one of the umpire

Umpire (baseball)

In baseball, the umpire is the person charged with officiating the game, including beginning and ending the game, enforcing the rules of the game and the grounds, making judgment calls on plays, and handling the disciplinary actions. The term is often shortened to the colloquial form ump...

s to make the ball call or the balk call immediately.