a person who likes making jokes or doing silly things to make people laugh 爱开玩笑的人；爱说笑话的人 He’s always been a bit of a joker. 他总是有点爱开玩笑。
- (informal)
a person that you think is stupid because they annoy you 蠢货；废人 an extra playing card that is used in some card games, usually as a wild card （某些纸牌游戏中的）百搭，（大、小）王牌 
Word Originearly 18th cent.: from the verb joke + -er.
Idioms
the joker in the pack
a person or thing that could change the way that things will happen in a way that cannot be predicted 能以意想不到的方式改变形势的人（或事）