/bɔ:l ||; bɔl/noun[C] 1 a round object that you hit, kick, throw, etc in games and sports 球: a tennis/golf/rugby ball 网球；高尔夫球；英式橄榄球a football 足球 ☞pictures at pool and sport 见pool及sport插图
2 a round object or a thing that has been formed into a round shape 球状物体: a ball of wool 毛线团The children threw snowballs at each other. 孩子们互相投掷雪球。We had meatballs and pasta for dinner. 我们晚餐吃肉丸和面食。
3 one throw, kick, etc of the ball in some sports （某些运动中的）一次投球、踢球等: That was a great ball from the defender. 防守球员踢了一个妙球。
4 a large formal party at which people dance 舞会
be on the ball(
informal 非正式) to always know what is happening and be able to react to or deal with it quickly 机敏；机警:
With so many new developments, you really have to be on the ball. 事态有了这么多新发展，你得保持机警。 set/start the ball rolling to start sth (an activity, conversation, etc) that involves or is done by a group 开个头；发起；发动:
I told a joke first, to set the ball rolling. 我先讲了个笑话，以抛砖引玉。