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[per-nish-uh s] /pərˈnɪʃ əs/
causing insidious harm or ruin; ruinous; injurious; hurtful:
pernicious teachings; a pernicious lie.
deadly; fatal:
a pernicious disease.
Obsolete. evil; wicked.
Origin of pernicious
1515-25; < Latin perniciōsus ruinous, equivalent to pernici(ēs) ruin (per- per- + -nici-, combining form of nex death, murder (stem nec-) + -iēs noun suffix) + -ōsus -ous
Related forms
perniciously, adverb
perniciousness, noun
unpernicious, adjective
unperniciously, adverb
1. harmful, detrimental, deleterious, destructive, damaging, baneful, noxious, malicious. 2. lethal. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2017.
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Examples from the Web for perniciously
Contemporary Examples
Historical Examples
  • Certain physiological processes come to have for him an unclean flavour which is yet perniciously attractive.

    The Nervous Child Hector Charles Cameron
  • He explained that Allen had been a feeble speculator, but plausible, of personal good faith, and perniciously sanguine.

  • And probably I've behaved more foolishly and perniciously than ever you will.

  • These indefinite expressions operated powerfully and perniciously on his imagination.

  • In these matters his aims were generous, if his methods were perniciously mistaken.

    Shelley Francis Thompson
  • He approached me with outstretched hand; he was perniciously polite; his ingratiating smile fired my soul with a lust of blood.

  • Thou hast devilishly and perniciously abstained from coming to church, and thou hast been guilty of the sin of preaching.

    The Coming of the King James Hocking
  • He wore outside a dogged look, as if fighting against some inward feeling; he entered looking down most perniciously at the floor.

  • In the case of truth, untrue beliefs work as perniciously in the long run as true beliefs work beneficially.

    Pragmatism William James
British Dictionary definitions for perniciously


wicked or malicious: pernicious lies
causing grave harm; deadly
Derived Forms
perniciously, adverb
perniciousness, noun
Word Origin
C16: from Latin perniciōsus, from perniciēs ruin, from per- (intensive) + nex death
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
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Word Origin and History for perniciously



early 15c., from Middle French pernicios (13c., Modern French pernicieux) and directly from Latin perniciosus "destructive," from pernicies "destruction, death, ruin," from per- "completely" (see per) + necis "violent death, murder," related to necare "to kill," nocere "to hurt, injure, harm," noxa "harm, injury" (see noxious). Related: Perniciously; perniciousness.

Online Etymology Dictionary, © 2010 Douglas Harper
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perniciously in Medicine

pernicious per·ni·cious (pər-nĭsh'əs)
Tending to cause death or serious injury; deadly.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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