A double play occurs when two offensive players are ruled out within the same play. It's often referred to as "a pitcher's best friend" because it's twice as helpful toward his cause as any given out.
Double plays can be made in any number of ways, but the most common form is on a ground ball with a runner on first. In this case, the defense typically throws the ball to second base to get the first out before throwing the ball to first base for the second out.
A double play can be recorded on a flyout if a fielder throws out a runner who strayed off his base or was trying to advance. Double plays also don't necessarily need to feature a force out at second. If the defense gets the out at first base, then tags another runner out on the bases, that counts as a double play as well.
Pitchers who record the highest number of double plays typically induce a high frequency of ground balls. And defenses that are adept at turning double plays generally have two very good middle infielders who are skilled at both starting the double play and at making a quick catch and throw from second base.
Watch: The Reds infield turns a double play.
In A Call
"turned two," "doubled up," "twin killing," "pitcher's best friend"