insidious

• POS: Adjective
• HYPHEN: in=sid=i=ous

CIDE DICTIONARY

insidious, a. [L. insidiosus, fr. insidiae an ambush, fr. insidere to sit in; pref. in- + sedere to sit: cf. F. insidieux. See Sit.].

•  Lying in wait; watching an opportunity to insnare or entrap; deceitful; sly; treacherous; -- said of persons; as, the insidious foe.  Cowper.  [1913 Webster]
•  Intended to entrap; characterized by treachery and deceit; as, insidious arts.  [1913 Webster]

  "The insidious whisper of the bad angel."  [1913 Webster]
•  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.

OXFORD DICTIONARY

insidious, adj.
1 proceeding or progressing inconspicuously but harmfully (an insidious disease).
2 treacherous; crafty.

Derivative

insidiously adv. insidiousness n.

Etymology

L insidiosus cunning f. insidiae ambush (as IN-(2), sedere sit)

THESAURUS

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

ROGET THESAURUS

insidious

Cunning

N cunning, craft, cunningness, craftiness, subtlety, artificiality, maneuvering, temporization, circumvention, chicane, chicanery, sharp practice, knavery, jugglery, concealment, guile, doubling, duplicity, foul play, diplomacy, politics, Machiavelism, jobbery, backstairs influence, art, artifice, device, machination, plot, maneuver, stratagem, dodge, sidestep, artful dodge, wile, trick, trickery, ruse, ruse de guerre, finesse, side blow, thin end of the wedge, shift, go by, subterfuge, evasion, white lie, juggle, tour de force, tricks of the trade, tricks upon travelers, espieglerie, net, trap, Ulysses, Machiavel, sly boots, fox, reynard, Scotchman, Jew, Yankee, intriguer, intrigant, floater, Indian giver, keener, repeater, cunning, crafty, artful, skillful, subtle, feline, vulpine, cunning as a fox, cunning as a serpent, deep, deep laid, profound, designing, contriving, intriguing, strategic, diplomatic, politic, Machiavelian, timeserving, artificial, tricky, tricksy, wily, sly, slim, insidious, stealthy, underhand, subdolous, deceitful, slippery as an eel, evasive, crooked, arch, pawky, shrewd, acute, sharp, sharp as a tack, sharp as a needle, canny, astute, leery, knowing, up to snuff, too clever by half, not to be caught with chaff, tactful, diplomatic, politic, polite, cunningly, slyly, slily, on the sly, by a side wind, diamond cut diamond, a' bis ou a blanc, fin contre fin, something is rotten in the state of Denmark.

Improbity

N improbity, dishonesty, dishonor, deviation from rectitude, disgrace, fraud, lying, bad faith, Punic faith, mala fides, Punica fides, infidelity, faithlessness, Judas kiss, betrayal, breach of promise, breach of trust, breach of faith, prodition, disloyalty, treason, high treason, apostasy, nonobservance, shabbiness, villainy, villany, baseness, abjection, debasement, turpitude, moral turpitude, laxity, trimming, shuffling, perfidy, perfidiousness, treachery, double dealing, unfairness, knavery, roguery, rascality, foul play, jobbing, jobbery, graft, bribery, venality, nepotism, corruption, job, shuffle, fishy transaction, barratry, sharp practice, heads I win tails you lose, mouth honor, dishonest, dishonorable, unconscientious, unscrupulous, fraudulent, knavish, disgraceful, wicked, false-hearted, disingenuous, unfair, one-sided, double, double- hearted, double-tongued, double-faced, timeserving, crooked, tortuous, insidious, Machiavelian, dark, slippery, fishy, perfidious, treacherous, perjured, infamous, arrant, foul, base, vile, ignominious, blackguard, contemptible, unrespectable, abject, mean, shabby, little, paltry, dirty, scurvy, scabby, sneaking, groveling, scrubby, rascally, pettifogging, beneath one, low-minded, low-thoughted, base-minded, undignified, indign, unbecoming, unbeseeming, unbefitting, derogatory, degrading, infra dignitatem, beneath one's dignity, ungentlemanly, ungentlemanlike, unknightly, unchivalric, unmanly, unhandsome, recreant, inglorious, corrupt, venal, debased, mongrel, faithless, of bad faith, false, unfaithful, disloyal, untrustworthy, trustless, trothless, lost to shame, dead to honor, barratrous, dishonestly, mala fide, like a thief in the night, by crooked paths, Int, O tempora!, O mores!, corruptissima respublica plurimae leges.

Deception

N deception, falseness, untruth, imposition, imposture, fraud, deceit, guile, fraudulence, fraudulency, covin, knavery, misrepresentation, bluff, straw-bail, straw bid, spoof, delusion, gullery, juggling, jugglery, slight of hand, legerdemain, prestigiation, prestidigitation, magic, conjuring, conjuration, hocus-pocus, escamoterie, jockeyship, trickery, coggery, chicanery, supercherie, cozenage, circumvention, ingannation, collusion, treachery, practical joke, trick, cheat, wile, blind, feint, plant, bubble, fetch, catch, chicane, juggle, reach, hocus, bite, card sharping, stacked deck, loaded dice, quick shuffle, double dealing, dealing seconds, dealing from the bottom of the deck, artful dodge, swindle, tricks upon travelers, stratagem, confidence trick, fake, hoax, theft, ballot-box stuffing, barney, brace game, bunko game, drop game, gum game, panel game, shell game, thimblerig, skin game, snare, trap, pitfall, decoy, gin, springe, springle, noose, hoot, bait, decoy-duck, tub to the whale, baited trap, guet-a-pens, cobweb, net, meshes, toils, mouse trap, birdlime, dionaea, Venus's flytrap, ambush, trapdoor, sliding panel, false bottom, spring-net, spring net, spring gun, mask, masked battery, mine, flytrap, green goods, panel house, Cornish hug, wolf in sheep's clothing, disguise, disguisement, false colors, masquerade, mummery, borrowed plumes, pattes de velours, mockery, copy, counterfeit, sham, make- believe, forgery, fraud, lie, a delusion a mockery and a snare, hollow mockery, whited sepulcher, painted sepulcher, tinsel, paste, junk jewelry, costume jewelry, false jewelry, synthetic jewels, scagliola, ormolu, German silver, albata, paktong, white metal, Britannia metal, paint, veneer, jerry building, man of straw, illusion, ignis fatuus, mirage, deceived, deceiving, cunning, prestigious, prestigiatory, deceptive, deceptious, deceitful, covinous, delusive, delusory, illusive, illusory, elusive, insidious, ad captandum vulgus, untrue, mock, sham, make-believe, counterfeit, snide, pseudo, spurious, supposititious, so-called, pretended, feigned, trumped up, bogus, scamped, fraudulent, tricky, factitious bastard, surreptitious, illegitimate, contraband, adulterated, sophisticated, unsound, rotten at the core, colorable, disguised, meretricious, tinsel, pinchbeck, plated, catchpenny, Brummagem, artificial, synthetic, ersatz, simulated, under false colors, under the garb of, under cover of, over the left, keep the word of promise to the ear and break it t, fronti nulla fides, ah that deceit should steal such gentle shapes, a quicksand of deceit, decipimur specie recti, falsi crimen, fraus est celare fraudem, lupus in fabula, so smooth, he daubed his vice with show of virtue.