Balk

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.

Read more about Balk:  Balk Actions, Clarifications, Common Misconceptions, Major League Balk Records, Famous Balks