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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. 2018.
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Examples from the Web for perniciously
Contemporary Examples
Historical Examples
  • And probably I've behaved more foolishly and perniciously than ever you will.

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

    Shelley Francis Thompson
  • He explained that Allen had been a feeble speculator, but plausible, of personal good faith, and perniciously sanguine.

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

  • But Supermanism is heresy, and it rapidly spread over the world, most perniciously influencing all intellectual life.

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

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

  • The privilege has been withdrawn as one perniciously against the tenets of the church.

    Tess of the Storm Country

    Grace Miller White
  • He did both these things, poor man, for it was his rôle in life always to say and do the perniciously obvious.

    The Halo Bettina von Hutten
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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