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.
Lauren Leffer, Popular Science, 14 Aug. 2024
Last is the most insidious prong of overtourism: when locals do not sufficiently benefit from tourism in their communities, due to unequal distribution of profits.
—Marco Quiroz-Gutierrez, Fortune Europe, 12 Aug. 2024
Environmental change is often insidious and unseen.
—Kelly Presutti, ARTnews.com, 2 Aug. 2024
These stereotypes have evolved to become more insidious, now showing up as the constantly pregnant welfare queen with multiple baby daddies, the bitter single career woman, and the Black woman who lives life in service of everyone but herself.
—Essence, 1 Aug. 2024
See all Example Sentences for insidious 
These examples are programmatically compiled from various online sources to illustrate current usage of the word 'insidious.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.
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Cite this Entry
“Insidious.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/insidious. Accessed 20 Aug. 2024.
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insidious
adjective
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insidious
adjective
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