An action in baseball taken by a baserunner following a fly ball out, in which the baserunner touches his time-of-pitch base and attempts to advance to the next base before he can be tagged out.
Immediately following a fly ball caught by an outfielder, a runner on any base can touch (tag) that base and attempt to take the next base. The ball is still considered live and the runner must reach the next base safely before any tag by a defensive player is applied. A defensive player can tag the runner or touch the base the runner was originally at if he believes that the player did not tag up, or left the base before the fly ball was caught. If this appeal is approved by a member of the umpiring crew, the runner is called out. Runners may tag up even when a ball is caught in foul territory. When a player tags up at third base and comes in to score, the batter who made the fly ball out is credited with a sacrifice fly.