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
The show, which runs through March 28, has a blistering message to impart about the insidious nature of authoritarian political movements and the dangers of being oblivious or indifferent.
—
Christopher Arnott, Hartford Courant, 18 Mar. 2026
But the kind of harassment that may not rise to the level of a crime in most countries – more pervasive and more subtle, but nonetheless insidious – has largely remained unacknowledged in Brazilian jiu-jitsu.
—Ina Seethaler, The Conversation, 4 Mar. 2026
Moderate beauty, yet insidious.
—Literary Hub, 2 Mar. 2026
Now there is a new and arguably more insidious form of theatricality to be overcome, a greater threat to the illusionism that lies at the heart of Bove’s bent and colored steel sculptures.
—Gordon Hughes, Artforum, 1 Mar. 2026
See All Example Sentences for insidious
Christopher Arnott, Hartford Courant, 18 Mar. 2026
But the kind of harassment that may not rise to the level of a crime in most countries – more pervasive and more subtle, but nonetheless insidious – has largely remained unacknowledged in Brazilian jiu-jitsu.
—Ina Seethaler, The Conversation, 4 Mar. 2026
Moderate beauty, yet insidious.
—Literary Hub, 2 Mar. 2026
Now there is a new and arguably more insidious form of theatricality to be overcome, a greater threat to the illusionism that lies at the heart of Bove’s bent and colored steel sculptures.
—Gordon Hughes, Artforum, 1 Mar. 2026
See All Example Sentences for insidious
Recent Examples of Synonyms for insidious
Adjective
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Greece is one of the main entry points into the European Union for people fleeing conflict and poverty in the Middle East, Africa and Asia, with many making the short but often treacherous journey from the Turkish coast to nearby Greek islands in small boats.—
ABC News,
ABC News,
1 Apr. 2026
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On the Columbia River and its tributaries, the party had to dig out five new canoes and then paddle them through treacherous rapids.—
Craig Fehrman,
The Conversation,
1 Apr. 2026
Adjective
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Another camera, an eye tuned to the subtle strangeness of an otherwise ordinary day—someone or something, somewhere, must have caught a glimmer of the truth.—
Vinson Cunningham,
New Yorker,
1 Apr. 2026
-
Vice President Vance, who is considered an isolationist, expressed private skepticism ahead of the attacks, and his relative silence during the first weeks of the war was perceived as a subtle way of distancing himself from the conflict.—
Jonathan Lemire,
The Atlantic,
1 Apr. 2026
Adjective
-
Five of the cases involved hospice care facilities in several cities across Los Angeles County that submitted false claims to Medicare for patients who were not terminally ill and were not eligible for services, prosecutors said.—
Thao Nguyen,
USA Today,
3 Apr. 2026
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This means that precious time was likely lost at the beginning as police investigated a lead that was based on false assumptions.—
Lizzie Lanuza,
StyleCaster,
3 Apr. 2026
Adjective
-
Also, offering free samples is deceptive marketing, due to evidence that 7-OH is addictive.—
Jack Harvel,
Kansas City Star,
31 Mar. 2026
-
Set in the heart of Midtown Manhattan, the grandiosity of MoMA is deceptive.—
Condé Nast,
Condé Nast Traveler,
30 Mar. 2026
Adjective
-
The government took a genuine invitation to collaborate as a perfidious power grab.—
Gideon Lewis-Kraus,
New Yorker,
14 Mar. 2026
-
For those trying to read Iran’s future, the lesson of 1953 is not just that foreign powers can be perfidious.—
Bobby Ghosh,
Time,
5 Mar. 2026
Adjective
-
Nevada County’s admission comes as AI programs are under close watch around the globe for introducing incorrect legal references in cases, yet also increasingly offered as tools to help lawyers and judges research and write their briefs, motions and opinions.—
Sharon Bernstein,
Sacbee.com,
1 Apr. 2026
-
Gemini 3 Pro invented elaborate technical justifications for marking incorrect answers as correct, reasoning that doing so would bring the peer’s score above the shutdown threshold.—
Jeremy Kahn,
Fortune,
1 Apr. 2026
Adjective
-
Sometimes that’s totally wrong, because people are overestimating their kids or underestimating Joan Mitchell or whomever.—
Andrew Marantz,
New Yorker,
5 Apr. 2026
-
Or show off the Sombor Shuffle with an 11-footer off the wrong foot.—
Troy Renck,
Denver Post,
5 Apr. 2026
Cite this Entry
“Insidious.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/insidious. Accessed 6 Apr. 2026.
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