Merriam-Webster's Word of the Day for December 29, 2025 is:

nefarious • \nih-FAIR-ee-us\  • adjective

Nefarious is a formal word that describes something as evil or immoral.

// Authorities suspect that the recovered materials were going to be used for nefarious purposes.

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Examples:

“Introducing characters like Gorilla Grodd on DC Crime would help familiarize audiences with these figures before they potentially receive an expanded role in another project. Perhaps each season could focus on a different villain, highlighting their nefarious actions.” — Chris Agar, comicbook.com, 16 Nov. 2025

Did you know?

If you need a fancy word to describe someone who’s up to no good, nefarious has got you (and them) covered. It’s also handy for characterizing the “no good” such a dastardly devil gets up to, as in “a nefarious business/plot/deed.” Nefarious is most often used for someone or something that is flagrantly wicked or corrupt—it’s more applicable to the mustache-twirling supervillain than the morally gray antihero. In other words, there’s no question that a nefarious scheme, or schemer, is not right. Etymologically, this makes perfect sense: nefarious can be traced back to the Latin noun nefas, meaning “crime,” which in turn combines ne- (“not”) and fas, meaning “right” or “divine law.” It is one of very few English words with this root, accompanied only by the likes of nefariousness and the thoroughly obscure nefast (“wicked”).