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 &imacron;nsidi&omacron;sus, from &imacron;nsidiae, ambush, from &imacron;nsid&emacron;re, to sit upon, lie in wait for : in-, in, on; see in–2 + sed&emacron;re, 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”).