- 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 of insidiousClassical Latin insidiosus ; from insidiae, an ambush, plot ; from insidere, to sit in or on, lie in wait for ; from in-, in + sedere, to sit
- 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 of insidiousFrom 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.
(comparative more insidious, superlative most insidious)