Definition
used to express that you believe what someone has just said is unreasonable or unfair.
你在開玩笑吧（表示不同意或覺得對方在說荒唐的話）
"This jacket costs £1000?" You're having a laugh!
「這件夾克要1000英鎊？」你在開玩笑吧！
You say you'll finish the project in a week? You're having a laugh!
你說你一周內能完成這個項目？你在開玩笑吧！
They want us to work for free, you're having a laugh!
他們想讓我們免費工作，你在開玩笑吧！