From The Collaborative International Dictionary of English v.0.44 [gcide]:
Insidious \In*sid"i*ous\, adjective [L. insidiosus, fr. insidiae an ambush, fr. insidere to sit in; pref. in- + sedere to sit: cf. F. insidieux. See {Sit}.]
1. Lying in wait; watching an opportunity to insnare or entrap; deceitful; sly; treacherous; -- said of persons; as, the insidious foe. ''The insidious witch.'' --Cowper.
2. Intended to entrap; characterized by treachery and deceit; as, insidious arts.
The insidious whisper of the bad angel. --Hawthorne.
3. Acting or proceeding unobserved or in a seemingly harmless manner, but slowly or eventually doing great damage; as, an insidious disease; an insidious plot. [PJC]
{Insidious disease} (Med.), a disease existing, without marked symptoms, but ready to become active upon some slight occasion; a disease not appearing to be as bad as it really is.
Syn: Crafty; wily; artful; sly; designing; guileful; circumventive; treacherous; deceitful; deceptive. -- {In*sid"i*ous*ly}, adverb -- {In*sid"i*ous*ness}, noun
From WordNet (r) 2.0 [wn]:
adjective
1: beguiling but harmful; "insidious pleasures"
3: working or spreading in a hidden and usually injurious way; "glaucoma is an insidious disease"; "a subtle poison" [syn: {pernicious}, {subtle}]
From Moby Thesaurus II by Grady Ward, 1.0 [moby-thes]:
106 Moby Thesaurus words for "insidious": Byzantine, Machiavellian, Machiavellic, acute, amoral, arch, artful, astute, cagey, calculating, canny, chiseling, clever, collusive, conscienceless, corrupt, corrupted, covinous, crafty, criminal, crooked, cunning, cute, dangerous, dark, deceitful, deep, deep-laid, designing, devious, diplomatic, dishonest, dishonorable, doubtful, dubious, evasive, false, falsehearted, feline, felonious, finagling, fishy, foxy, fraudulent, furtive, gradual, guileful, ill-got, ill-gotten, immoral, indirect, ingenious, inventive, knowing, not kosher, pawky, perfidious, perilous, politic, questionable, ready, resourceful, rotten, scheming, serpentine, shady, shameless, sharp, shifty, shrewd, sinister, slick, slippery, sly, smooth, snaky, sneaky, sophistical, stealthy, strategic, subtile, subtle, supple, surreptitious, suspicious, tactical, treacherous, trickish, tricksy, tricky, two-faced, unconscienced, unconscientious, unconscionable, underhand, underhanded, unethical, unprincipled, unsavory, unscrupulous, unstraightforward, vulpine, wary, wily, without remorse, without shame
Define.com is a registered nonprofit corporation dedicated solely to the global public interest and the advancement of humanity. It belongs to all of us who have a desire to promote electronic democracy, science, creativity, imagination, reason, critical thinking, peace, race and gender equality, civil rights, equal access to education, personal liberty, free speech, animal rights, compassionate and nonviolent parenting, social and economic justice, global monetary reform, Secular Humanism, cognitive liberty and a permanent cessation of The War on Drugs.
Let's see what we can do if we put our heads together.
0