Passed ball

From SoSH

A passed ball is a defensive miscue by the catcher on a pitch that allows a runner to advance at least one base. A passed ball should not be confused with a wild pitch, where the fault lies with the pitcher. A pitch is normally called a passed ball when the catcher is able to get his glove on the ball but fails to catch it cleanly.

The instances of passed balls have decreased with advances in the design of catcher's mitts.