Synonyms of insidious

1 Syllable

slyer, smooth, sly, slyest, slick, slier, wily, deep, sliest

2 Syllables

foxier, sneaking, shiftier, crooked, secret, witted, stealthy, corrupt, cunning, wilier, subtle, devious, foxy, unloyal, shiftiest, shifty, craftier, crafty, false, artful, dickens, snaky

3 Syllables

retiary, deceitful, vipery, astute, ensnaring, wormlike, treacherous, dishonest, guileful, lubricious, uncandid, mischievous, rascally, dangerous, perfidious, furtive, designing, underhand, perilous, intriguing

4 Syllables

duplicitous, falsehearted, machiavellian, ill-behaved, deceptive, dirty-dealing, disingenuous, surreptitious

6 Syllables

prevaricatory