Simple Definition of insidious
: causing harm in a way that is gradual or not easily noticed
Full Definition of insidious
Examples of insidious
But the litigation is also prompting a subtle and insidious change in the way that medicine is practiced, which affects anyone who consults a health professional, even if they would not dream of setting foot in a lawyer's office. It is known as “defensive medicine.” —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.
Origin of insidious
Latin insidiosus, from insidiae ambush, from insidēre to sit in, sit on, from in- + sedēre to sit — more at sit
First Known Use: 1545
Medical Definition of insidious
: developing so gradually as to be well established before becoming apparent <an insidious disease>
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