Verb
tag up (third-person singular simple present tags up, present participle tagging up, simple past and past participle tagged up)
(baseball) Of a baserunner, when a fly ball is hit, to put one's foot on the base one is currently at until the ball is caught. When the ball is caught, the baserunner may attempt to advance to the next base, at the risk of being tagged out.
If the fielder bobbles the ball, the runner may still tag up, even before the fielder has full control of the ball (before the fielder is credited with a putout). Source: Internet
If the ball is hit in the air and caught before it lands, the batter has flied out and any runners on base may attempt to advance only if they tag up or touch the base they were at when the play began, as or after the ball is caught. Source: Internet