English Reference

Word

nefarious

Phoneticsne·far·i·ous

US/nəˈfɛɹiəs/

UK/nəfˈeəɹɪəs/

Definition

adj. describing something that is very bad, dishonest, or illegal. You use this to talk about activities that people do to hurt others or break the law.

adj. describing actions or intentions that are wicked, dishonest, or illegal. Often used to describe organized crime or secret plots.

Examples

“The group was involved in nefarious activities.”

“The detective spent months investigating the nefarious dealings of the local gang.”

“The novel explores the nefarious influence of corporate lobbying on the democratic process, suggesting that the pursuit of profit often overrides the public good.”

Examples

simple

“The group was involved in nefarious activities.”

contextual

“The detective spent months investigating the nefarious dealings of the local gang.”

complex

“The novel explores the nefarious influence of corporate lobbying on the democratic process, suggesting that the pursuit of profit often overrides the public good.”

Real-World Examples

“The Reformers and others involved, like Anita Perrottet, deny that these payments were nefarious and argue instead that they actually did real consulting or lobbying work.”
The Guardian · 28 Aug 2026
“Then there’s the more nefarious activities – I’ve heard of researchers deliberately moving specimens to make them hard to find so other researchers cannot examine them, and occasionally things are stolen from collections.”
ScienceDaily · 7 Aug 2026
“Though a mutated gene sounds nefarious, most of these natural alterations in the genome don’t have much effect on their hosts.”
Smithsonian Magazine · 25 Feb 2016

Etymology

From Latin nefārius (“execrable, abominable”), from nefās (“something contrary to divine law, an impious deed, sin, crime”), from ne- (“not”) + fās (“the dictates of religion, divine law”), which is related to Latin for (“to speak, to say”) and cognate to Ancient Greek φημί (phēmí, “to say”).

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry

Level
C1 · Advanced
Frequency
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