- The definition of insidious is something or someone who works in a subtle or sly way, or in an intent to trap.
An example of insidious is a plan that is meant to scam people out of money.
- characterized by treachery or slyness; crafty; wily
- operating in a slow or not easily apparent manner; more dangerous than seems evident: an insidious disease
Origin: L insidiosus from insidiae, an ambush, plot from insidere, to sit inch(es) or on, lie inch(es) wait for from in-, inch(es) plush sedere, to sit
Used by arrangement with John Wiley & Sons, Inc.
- Working or spreading harmfully in a subtle or stealthy manner: insidious rumors; an insidious disease.
- Intended to entrap; treacherous: insidious misinformation.
- Beguiling but harmful; alluring: insidious pleasures.
Origin: From Latin īnsidiōsus, from īnsidiae, ambush, from īnsidēre, to sit upon, lie in wait for : in-, in, on; see in-2 + sedēre, to sit; see sed- in Indo-European roots.
- in·sidˈi·ous·ly adverb
- in·sidˈi·ous·ness noun
insidious - Medical Definition
- insidiously adverb