as in treacherous
formal
causing harm in a way that is gradual or not easily noticed
Most people with this insidious disease have no idea that they are infected. an insidious enemy
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Recent Examples of insidious
Months later, scientists discovered something far more insidious: The volcano had caused an unexpected seismic reaction that released hazardous levels of CO2 – once trapped in the ground – into the air.
—
Colette Davidson, Christian Science Monitor, 14 Apr. 2025
But beyond this damage lies something more insidious: democratic backsliding.
—Nicholas Creel, MSNBC Newsweek, 5 May 2025
Some marriages don’t unravel through conflict — they get caught in a more insidious, exhausting loop.
—Mark Travers, Forbes.com, 4 May 2025
In humans, the infection is insidious, with an asymptomatic incubation period of between 5 and 15 years.
—ArsTechnica, 23 Apr. 2025
See All Example Sentences for insidious
Colette Davidson, Christian Science Monitor, 14 Apr. 2025
But beyond this damage lies something more insidious: democratic backsliding.
—Nicholas Creel, MSNBC Newsweek, 5 May 2025
Some marriages don’t unravel through conflict — they get caught in a more insidious, exhausting loop.
—Mark Travers, Forbes.com, 4 May 2025
In humans, the infection is insidious, with an asymptomatic incubation period of between 5 and 15 years.
—ArsTechnica, 23 Apr. 2025
See All Example Sentences for insidious
Recent Examples of Synonyms for insidious
Adjective
-
Hickey made three trips back and forth in the treacherous water to save the boaters one by one.—
Nicholas Williams,
New York Daily News,
25 May 2025
-
Mastering wet roads: Safety tips for heavy rainfall When heavy rain pours, the risk of flooding and treacherous roads rises.—
Southern California Weather Report,
Oc Register,
24 May 2025
Adjective
-
Arthritis in your fingers often starts with subtle changes.—
Brandi Jones,
Health,
25 May 2025
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The navy, white, and subtle red palette nods to the seaside and seamlessly blends into Printemps' signature French elegance.—
Roxanne Robinson,
Forbes.com,
25 May 2025
Adjective
-
The decision to deploy Dembele as a false nine for a 3-1 home win over Lyon in mid-December proved the spark for a stupendous run of goal-scoring form in which the France international racked up 27 goals in only 22 appearances.—
Tom Williams,
New York Times,
30 May 2025
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Their accountant filed two false corporate tax returns, claiming one of the couple’s firms earned no money in 2015 and 2016.—
Howard Gleckman,
Forbes.com,
30 May 2025
Adjective
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During the defense’s cross-examination of Kid Cudi, lawyers representing Combs portrayed Ventura as deceptive of both men.—
Conor Murray,
Forbes.com,
22 May 2025
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California’s attorney general, Rob Bonta, filed a suit against ExxonMobil last year that, in part, accuses the oil giant of deceptive claims regarding chemical recycling, which the company disputes.—
Susanne Rust,
Los Angeles Times,
22 May 2025
Adjective
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Jake Gyllenhaal is his foil as the perfidious Iago, who goads Othello into unreasoning jealousy with lies about his beloved Desdemona (Molly Osborne).—
New York Times,
New York Times,
17 Feb. 2025
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Since then, Putin has sought instead to rally the public to the defense of a motherland besieged by the perfidious and cunning West.—
Leon Aron,
The Atlantic,
5 Dec. 2024
Adjective
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If a project fails because the decision to go ahead with the project turns out to be incorrect (which should happen frequently), that failure should not bear on the manager responsible for the project.—
Tim Koller,
Time,
20 May 2025
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The court had to issue a letter stating the interpretation was incorrect.—
Bob Carlson,
Forbes.com,
20 May 2025
Adjective
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For affluent Latino parents Enrique and Ilana Gomez, this moment goes hilariously wrong from the start, when their daughter Yoli invites her Mexican-born intended Marcos over to the family’s Pasadena home for dinner.—
Pam Kragen,
San Diego Union-Tribune,
30 May 2025
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But even putting O’Brien on notice would be an attempt to intimidate and silence a critic, which is plainly wrong.—
Sun Sentinel Editorial Board,
Sun Sentinel,
30 May 2025
Cite this Entry
“Insidious.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/insidious. Accessed 5 Jun. 2025.
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