An example of insidious is a plan that is meant to scam people out of money.
- characterized by treachery or slyness; crafty; wily
- working harm in a slow or subtle manner; hence, 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)
From Middle French insidieux, from Latin īnsidiōsus (“cunning, artful, deceitful”), from īnsidiae (“a lying in wait, an ambush, artifice, stratagem”) + -ōsus, from īnsideō (“to sit in or on”), from in (“in, on”) + sedeō (“to sit”).