- 1: a ridge of land left unplowed as a dividing line or through carelessness
- 2: beam, rafter
- 3: hindrance, check
- 4a : the space behind the balkline on a billiard table
- b : any of the outside divisions made by the balklines
- 5: failure of a player to complete a motion; especially : an illegal motion of the pitcher in baseball while in position
In baseball, a pitcher can commit a number of illegal motions or actions that constitute a balk. Most of these violations involve a pitcher pretending to pitch when he has no intention of doing so. 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. Under other rule sets, notably in the United States under the National Federation of High Schools (Fed or Federation) Baseball Rules, a balk results in an immediate dead ball. In the event a balk is enforced, the pitch is generally (but not always) nullified, each runner is awarded one base, and the batter (generally) remains at bat, and with the previous count. The balk rule in Major League Baseball was introduced in 1898.
A pitcher is restricted to a certain set of motions and one of two basic pitching positions before and during a pitch; if these regulations are violated with one or more runners on base, an umpire may call a balk.
With a runner on base and the pitcher on or astride (with one leg on each side of) the rubber, it is a balk when the pitcher:
- switches his pitching position from the windup to the set (or vice versa) without properly disengaging the rubber;
- while on the rubber, makes a motion associated with his pitch and does not complete the delivery;
- when pitching from the set position, fails to make a complete stop with his hands together before beginning to pitch;
- throws from the mound to a base without stepping toward (gaining distance in the direction of) that base;
- throws or feints a throw from the rubber to an unoccupied base, unless a play is imminent;
- steps or feints from the rubber to first or third base without completing the throw (doing so to second base is legal);
- delivers a quick return, a pitch thrown right after receiving the ball back, with intent to catch the batter off-guard;
- drops the ball while on the rubber, even if by accident, if the ball does not subsequently cross a foul line;
- while intentionally walking a batter, releases a pitch while the catcher is out of his box with one or both feet
- unnecessarily delays the game
- pitches while facing away from the batter;
- after bringing his hands together on the rubber, separates them except in making a pitch or a throw;
- stands on or astride the rubber without the ball, or mimics a pitch without the ball; or
- throws to first when the first baseman, because of his distance from the base, is unable to make a play on the runner there.
The pitcher's acts of spitting on the ball, defacing or altering the ball, rubbing the ball on the clothing or body, or applying a foreign substance to the ball are not balks, however it will result in the pitcher's ejection from the game if caught.