joker

1. N-COUNT Someone who is a joker likes making jokes or doing amusing things. 爱开玩笑; 逗趣的人

He is, by nature, a joker, a witty man with a sense of fun. 他天生是个爱开玩笑的人，是个有幽默感的风趣男人。

2. N-COUNT The joker in a deck of playing cards is the card that does not belong to any of the four suits. (纸牌中不属于任何一套花色的) 百搭牌

3. N-COUNT You can call someone a joker if you think they are behaving in a stupid or dangerous way. 家伙[非正式]

Keep your eye on these jokers, you never know what they will come up with. 盯住这些家伙，你永远不知道他们会想出什么来。