- intended to entrap or beguile: an insidious plan.
- stealthily treacherous or deceitful: an insidious enemy.
- operating or proceeding in an inconspicuous or seemingly harmless way but actually with grave effect: an insidious disease.
Origin of insidious
SynonymsSee more synonyms for on Thesaurus.com
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for insidious
The act of erasure through mis- or under-representation is an insidious one.It Ain't Easy Being Bisexual on TV
August 14, 2014
Its insidious reach enters into medical offices and chokes off the free-speech rights of the people trying to work there.Pediatricians Have the Right to Ask About Guns
July 30, 2014
Cancer is the most pernicious, insidious, disgusting disease of life.Pierce Brosnan’s Life After Bond: From Action Hero to Losing His Daughter to Cancer
July 2, 2014
However, an insidious form of segregation, happening within the educational system, belies this simplistic view.Roma Children Face Segregation In EU Schools
March 8, 2014
This would be dismissible, but it actually had an insidious impact.Bob Woodward and the Rules of Washington Morality
March 3, 2013
Persuasive is the voice of Vice, That spreads the insidious snare.Philothea
Lydia Maria Child
The strong man must at all times be alert to the attack of insidious disease.
His delighted vanity found in it the most insidious of compliments, as she had intended.K
Mary Roberts Rinehart
She put Count Albert on his guard against this insidious enemy.Tales And Novels, Volume 8 (of 10)
This petition was an insidious blow at one of the most important of our industries.
- stealthy, subtle, cunning, or treacherous
- working in a subtle or apparently innocuous way, but nevertheless deadlyan insidious illness
C16: from Latin insidiōsus cunning, from insidiae an ambush, from insidēre to sit in; see insessorial
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
Word Origin and History for insidious
Online Etymology Dictionary, © 2010 Douglas Harper
- Being a disease that progresses with few or no symptoms to indicate its gravity.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.