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Synonyms

pernicious

American  
[per-nish-uhs] / pərˈnɪʃ əs /

adjective

  1. causing insidious harm or ruin; ruinous; injurious; hurtful.

    pernicious teachings;

    a pernicious lie.

    Synonyms:
    malicious, noxious, baneful, damaging, destructive, deleterious, detrimental, harmful
  2. deadly; fatal.

    a pernicious disease.

    Synonyms:
    lethal
  3. Obsolete. evil; wicked.


pernicious British  
/ pəˈnɪʃəs /

adjective

  1. wicked or malicious

    pernicious lies

  2. causing grave harm; deadly

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

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).

Keep Reading on Vocabulary.com

Vocabulary lists containing pernicious

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.

“Giant” is a probing character study that raises the discomfiting question of how a man of intelligence and imagination could hold such atavistic and pernicious views.

From The Wall Street Journal • Mar. 24, 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

In his middle life, at about the time such things were known about, it was discovered that, he had pernicious anemia.

From "East of Eden" by John Steinbeck