in·sid·i·ous
/inˈsidēəs/
adjective
- proceeding in a gradual, subtle way, but with harmful effects.
synonyms: stealthy, subtle, surreptitious, sneaking, cunning, crafty, Machiavellian, artful, guileful, sly, wily, tricky, slick, deceitful, deceptive, dishonest, underhand, backhanded, indirect; informalsneaky"the insidious erosion of rights and liberties"- treacherous; crafty."tangible proof of an insidious alliance"
