We say a joke is "corny" if it is stupid.

如果一个笑话很蠢，我们会说它是“陈词滥调”。

youdao

Eight hours on a bus is no joke, is it.

坐８个小时的公交车可不是闹着玩儿的，对吧。

《柯林斯英汉双解大词典》

"It is no joke, Mr. Sesemann," replied the lady seriously.

“这不是开玩笑，赛赛曼先生。”小姐严肃地回答。

youdao

My brother is such a person. It is true C no joke.

VOA: special.2009.07.19

That seems like a bad joke,but if the body theory is right, it's not a joke at all.

又是一个冷笑话，但如果肉体主义者是对的，这就不是开玩笑了。

耶鲁公开课 - 死亡课程节选

Before you go, it is the weekend, I will send you off with a joke.

在离开之前，现在已经是周末了，我会给你们讲个笑话。

麻省理工公开课 - 固态化学导论课程节选

In fact, it is a common joke within the profession that you are better off saying you are an estate agent than health manager.

BBC: Is the NHS really over-managed?

It is a big joke.

FORBES: U.S. tax rackets

"A lot of people think it is a bit of a joke to see a postman being bitten by a dog but it is a serious matter, " said Mike Leach, a delivery office manager.

BBC: NEWS | UK | Wales | South East Wales | Mail campaign over dog attacks