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Definition of "insidious" []

  • Working or spreading harmfully in a subtle or stealthy manner: insidious rumors; an insidious disease. (adjective)
  • Intended to entrap; treacherous: insidious misinformation. (adjective)
  • Beguiling but harmful; alluring: insidious pleasures. (adjective)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Use "insidious" in a sentence
  • "I mean, you've got Darth Sidious (as in "insidious," I assume) and then the even-more-obviously named Darths Maul and Tyrannus."
  • "The greatest dangers to liberty lurk in insidious encroachment by men of zeal, well-meaning but without understanding."
  • "But I fear the most insidious is because people think that changing their lightbulbs and sorting their recyclables counts as “doing your bit”."