Synonyms

no-no

American

[noh-noh] / ˈnoʊˌnoʊ /

noun

Informal.

plural

no-nos, no-no's

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.

Etymology

Origin of no-no

1940–45, reduplication of no ¹

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

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

“Natural light is the best. I can’t do a dark house. The no-no of no-nos is bad floor plan and flow, and not enough natural light.”

From MarketWatch • Nov. 24, 2025

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

Another big no-no is showing up to work or events when you’re sick.

From Los Angeles Times • Oct. 2, 2024

She learned that golden retrievers are not ponies, peas taste funny, dead flies on the floor are a no-no, but candy is really good.

From "Out of My Mind" by Sharon M. Draper

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023