Caught stretching

From BR Bullpen

Caught stretching occurs when the batter-runner is put out while trying to extend a hit, usually a single, into an extra-base hit, usually a double.  In most instances, the player is tagged out at or near second base.  The batter is credited with a hit for the number of bases safely reached, but he is out. Any runs that score on the play before the out is made count, even if it is the third out in the inning. Similarly, if the batter hits the ball in front of an outfielder for what would normally have been only a single, but safely extends it into a double, he is said to have hit a "stretch double".  

Caught stretching and stretch double are not official statistics.