就是投球手準備投球時,已經在壘上的對方球員偷偷跑到下一個壘。是攻方的一個搶攻的辦法。防守方不可能偷壘的。
In baseball, a stolen base occurs when a runner advances to a base to which he is not entitled and the official scorer rules that the advance should be credited to the action of the runner. ... A stolen base most often occurs when a baserunner advances to the next base while the pitcher is pitching the ball to home plate.