We don't have synonyms for tag up yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are bag up and tog up.
(v) :
(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.
(v) :
(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.