pernicious
Americanadjective
-
causing insidious harm or ruin; ruinous; injurious; hurtful.
pernicious teachings;
a pernicious lie.
- Synonyms:
- malicious, noxious, baneful, damaging, destructive, deleterious, detrimental, harmful
-
deadly; fatal.
a pernicious disease.
- Synonyms:
- lethal
-
Obsolete. evil; wicked.
adjective
-
wicked or malicious
pernicious lies
-
causing grave harm; deadly
Other Word Forms
- perniciously adverb
- perniciousness noun
- unpernicious adjective
- unperniciously adverb
Etymology
Origin of pernicious
First recorded in 1515–25; from Latin perniciōsus “ruinous,” from pernici(ēs) “ruin” (from per- per- + -nici-, combining form of nex “death, murder” + -ēs, noun suffix) + -ōsus -ous
Explanation
Pernicious means harmful and subtle, such as a poison gas that causes illness in those exposed to it over the course of years. Pernicious comes from the Latin perniciosus, "destructive," which in turn comes from pernicies, "death" or "ruin." You might have heard your parents and teachers talk about the pernicious effects of watching too much TV and playing video games all day — they'll turn your brain to mush (allegedly).
Vocabulary lists containing pernicious
Romeo and Juliet
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300 Most Difficult "SAT" Words
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The Tragedy of Hamlet, Prince of Denmark
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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.
“In an environment where you’re fighting for a promotion … It’s just a further incentive to agents to engage in this kind of activity. So it’s pernicious on multiple levels.”
From Salon • Apr. 6, 2026
High borrowing costs, he said, have had a pernicious impact on lower-income consumers without producing clear gains in inflation.
From Barron's • Jan. 26, 2026
A similarly pernicious logic has insulated law enforcement from legal accountability for generations.
From Slate • Jan. 25, 2026
The five-year bout of high inflation is part of the pernicious legacy of the coronavirus pandemic that began in 2020.
From MarketWatch • Jan. 23, 2026
Similarly, the pioneer of public education in Massachusetts, Horace Mann, believed that working students too hard would create a “most pernicious influence upon character and habits—Not infrequently is health itself destroyed by over-stimulating the mind.”
From "Outliers" by Malcolm Gladwell
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
