no-no

American  

[noh-noh] / ˈnoʊˌnoʊ /

noun

Informal.

no-nos, plural no-no's plural

1. anything that is forbidden or not advisable, as because of being improper or unsafe.

   If you want to lose weight, rich desserts are a no-no.

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Etymology

Origin of no-no

1940–45, reduplication of no ¹

Example Sentences

Putting EU money behind nuclear projects was long a no-no, with the 27-nation bloc focusing on renewables in the race to cut planet warming emissions.

From Barron's • Mar. 10, 2026

The biggest no-no: Uploading documents with personal information into a publicly available AI tool.

From MarketWatch • Feb. 17, 2026

Matthew Tkachuk, Sam Bennett and Brad Marchand, a trade deadline acquisition, throw insults in the face-off circle and make not-so-accidental contact with rival goalies—a serious no-no in hockey’s unwritten code.

From The Wall Street Journal • Jun. 18, 2025

He once got in trouble for bowing to a company executive with his hand in his pocket, a major no-no in Korean culture.

From Los Angeles Times • Nov. 6, 2024

“That’s a no-no, milady,” the imp said, a cold gleam in its eyes.

From "Half Upon a Time" by James Riley

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