from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Working or spreading harmfully in a subtle or stealthy manner: insidious rumors; an insidious disease.
- adj. Intended to entrap; treacherous: insidious misinformation.
- adj. Beguiling but harmful; alluring: insidious pleasures.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Producing harm in a stealthy, often gradual, manner.
- adj. Intending to entrap; alluring but harmful.
- adj. Treacherous.
from the GNU version of the Collaborative International Dictionary of English
- adj. Lying in wait; watching an opportunity to insnare or entrap; deceitful; sly; treacherous; -- said of persons.
- adj. Intended to entrap; characterized by treachery and deceit.
- adj. Acting or proceeding unobserved or in a seemingly harmless manner, but slowly or eventually doing great damage.
from The Century Dictionary and Cyclopedia
- Lying in wait; hence, deceitful; sly; treacherous.
- Designed or adapted to entrap; deceptive; insnaring: as, insidious arts.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adj. beguiling but harmful
- adj. intended to entrap
- adj. working or spreading in a hidden and usually injurious way
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.(American Heritage® Dictionary of the English Language, Fourth Edition)
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"). (Wiktionary)