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.
Education Secretary Bridget Phillipson said the pandemic had left a "pernicious legacy", but that teachers across the country were helping the next generation "turn a corner".
From BBC ● Jul. 9, 2026
In 2026, it is 100 years since George Minot and William Murphy reported that a liver-rich diet could treat pernicious anemia, then a frequently fatal disease.
From Science Daily ● Jun. 25, 2026
It would be unfair to depict Greenspan’s influence as invariably pernicious.
From Los Angeles Times ● Jun. 25, 2026
“For markets, the Strait is the only thing that matters, because its blockage was most pernicious for the global economy,” said Thierry Wizman, a strategist at Macquarie Group.
From MarketWatch ● Jun. 16, 2026
Radiation, in fact, is so pernicious and long lasting that even now her papers from the 1890s–even her cookbooks–are too dangerous to handle.
From "A Short History of Nearly Everything" by Bill Bryson
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.
