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Showing results for insidious. Search instead for insidiou.
Definitions

insidious

[in-sid-ee-uhs] / ɪnˈsɪd i əs /
ADJECTIVE
sneaky, tricky
Synonyms
STRONGEST
dangerous subtle
WEAK
Machiavellian artful astute corrupt crafty crooked cunning deceitful deceptive deep designing dishonest disingenuous duplicitous ensnaring false foxy guileful intriguing like a snake in the grass perfidious perilous secret slick sly smooth snaky sneaking stealthy surreptitious treacherous wily wormlike
Antonyms
WEAK
fair honest open sincere

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

Times columnist Patt Morrison, Smoglandia traces the rise, impact, and retreat of the city’s most insidious pollution.

From Los Angeles Times • Mar. 26, 2026

"The cold is a very insidious enemy, it should not be underestimated," she said.

From Barron's • Feb. 16, 2026

And while this image of a police chief is at odds with the much more varied and often insidious, violent truths of police work, Marge is a character torn right out of a Midwestern reality.

From Salon • Feb. 7, 2026

"In this series, we try to uncover the truth about what is beneath our feet, hear from the communities affected, and understand how something so insidious could stay buried for so long," Sheen added.

From BBC • Jan. 26, 2026

The abrupt stillness seemed alien and artificial, a little insidious.

From "Catch-22" by Joseph Heller

From Roget's 21st Century Thesaurus, Third Edition Copyright © 2013 by the Philip Lief Group.