a girl who picks up balls during a tennis, football or other sports game and gives them back to the players

The player gave his racket to a ball girl, which delighted the crowd. 球员把他的球拍送给了一个女球童，让观众非常高兴。

On Friday nights, she's a ball girl for the school's football team. 周五晚上，她给学校橄榄球队当女球童。