Meaning:

Literally meaning “big smart,” this term is however used sarcastically by Chinese netizens to imply that someone is stupid. The Chinese phrase was used as the name of a character from the 2018 comedy “Hello, Mr. Billionaire.” In that movie, Wang Chengsi plays the role of Da Cong Ming, a stupid but lucky guy who has earned a lot of money by sheer luck.

Example:

A: 听说老板有个亲戚来公司管你们市场部。

Tīngshuō lǎobǎn yǒu ge qīnqī lái gōngsī guǎn nǐmen shìchǎngbù？

I’ve heard that a relative of the boss will join the company and run your marketing department.

B: 是的，昨天来上班了，听他的自我介绍感觉是个大聪明。

Shì de ，zuótiān lái shàngbān le，tīng tā de zìwǒ jièshào gǎnjué shì ge dàcōngming。

It’s true. He came to the office yesterday, but after hearing his self introduction, I feel he’s kinda stupid.