劍橋詞典the practice of having a lot of balls available to use during a football game , any of which quickly replace the ball that is being used when it goes outside the playing area during the game （足球比賽中準(zhǔn)備好多個(gè)球，在比賽用球出界時(shí)可隨時(shí)替換的）多球系統(tǒng) 返回 multiball system