- 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 on Thesaurus.com
1. corrupting. 2. artful, cunning, wily, subtle, crafty.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for insidiously
Others, more quietly but just as insidiously, operate from the Muslim religious right.Arab Americans Need Political Normalization
November 12, 2012
Are you insidiously advised or tempted to contract it, by any one?Life And Adventures Of Martin Chuzzlewit
And thus a dead point in the revolution of my affairs was insidiously got over.An Outcast of the Islands
Slowly and insidiously it had come to dominate every other problem.
"Better in health, because better in spirits," said the housekeeper, insidiously.Jack Harkaway's Boy Tinker Among The Turks
"There," said Miss Baker, insidiously giving the man two and threepence.The Bertrams
- 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 insidiously
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.