Dictionary.com
Thesaurus.com
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

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.