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
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.
Dahlia Lithwick: Election law expert Rick Hasen just described this as “one of the most pernicious and damaging Supreme Court decisions of the past century.”
From Slate • Apr. 30, 2026
“When something is consistently wrong, the good thing is you know not to trust it. But when things are mostly right but sometimes wrong, that’s the most pernicious one.”
From The Wall Street Journal • Apr. 14, 2026
“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
Grube told me that he thought the kings of Kaan, never allied with Teotihuacan, may have wanted to stamp out pernicious foreign influences—xenophobia is a powerful motive in every culture.
From "1491" by Charles C. Mann
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.
