insidious
adjective
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insidious, sinister, or pernicious?
Few would choose to be associated with people or things that are insidious, sinister, or pernicious; all three of these words have decidedly unpleasant meanings, each with its own particular shade of nastiness.
Insidious comes from a Latin word for “ambush” (insidiae), which is fitting, as this word often carries the meanings “deceitful,” “stealthy,” or “harmful in an imperceptible fashion.” The first two meanings may be applied to people or things (“an insidious enemy,” “an insidious plot”), while the last is usually applied to things (“insidious problems,” “insidious sexism”), in particular to the gradual progress of a disease (“an insidious malignancy”).
Sinister comes from a Latin word meaning “on the left side, unlucky, inauspicious.” Although it is commonly used today in the sense “evil” (“a sinister cult leader”; “a sinister plot”), it may also suggest an ominous foreshadowing of some unfavorable turn of events (“a sinister omen”).
Pernicious has largely stayed true to its etymological root, the Latin noun pernicies “ruin, destruction.” Its original meaning in English, “highly injurious or destructive,” usually applies to things (“pernicious apathy,” “pernicious effects”) and medical conditions (“pernicious fever,” “pernicious anemia”). When applied to people, pernicious means “wicked.”
Examples of insidious in a Sentence
Geoff Watts, New Scientist, 23–29 Oct. 2004
Spin is sometimes dismissed as a simple euphemism for lying. But it's actually something more insidious: indifference to the truth.
—Michael Kinsley, Time, 25 Dec. 2000–1 Jan. 2001
As these boats aged and bedding compounds deteriorated, the water torture began, which led to rot, corrosion, and other insidious problems.
—Ralph Naranjo, Cruising World, April 1999
Most people with this insidious disease have no idea that they are infected.
Willie Wilson, Chicago Tribune, 27 Mar. 2025
Through that longtime relationship and writing Caddy for Life about Edwards, who died from ALS in 2004, Feinstein became dedicated to fighting the insidious disease — including donating half the profits of the book that became one of his 23 to land on The New York Times bestseller list.
—Vahe Gregorian, Kansas City Star, 26 Mar. 2025
But the insidious nature of the illness rendered those efforts fruitless.
—Orlando Sentinel and Virginian Pilot Editorial Boards, The Orlando Sentinel, 26 Mar. 2025
In a hybrid world, where our online and offline lives are increasingly interwoven, the erosion of agency can manifest in insidious ways.
—Cornelia C. Walther, Forbes, 22 Mar. 2025
See All Example Sentences for insidious
Cite this Entry
“Insidious.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/insidious. Accessed 1 Apr. 2025.
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insidious
adjective
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insidious
adjective
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