insidious

The definition of insidious is something or someone who works in a subtle or sly way, or in an intent to trap.

(adjective)

An example of insidious is a plan that is meant to scam people out of money.

See insidious in Webster's New World College Dictionary

adjective

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 < insidiae, an ambush, plot < insidere, to sit in or on, lie in wait for < in-, in + sedere, to sit

Related Forms:

See insidious in American Heritage Dictionary 4

adjective

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:

Origin: From Latin īnsidiōsus

Origin: , from īnsidiae, ambush

Origin: , from īnsidēre, to sit upon, lie in wait for

Origin: : in-, in, on; see in-²

Origin: + sedēre, to sit; see sed- in Indo-European roots

Related Forms: