underhanded

1 given to or marked by cheating and deception the commercial is a part of an underhanded PR campaign to whitewash the company's environmental record Synonyms bent [chiefly British], crooked, deceptive, double-dealing, duplicitous, fast, fraudulent, guileful, rogue, shady, sharp, shifty, underhand, dishonestRelated Words unconscionable, unethical, unprincipled, unscrupulous; deceitful, deceiving, deluding, delusive, delusory, false; artful, beguiling, cagey (also cagy), crafty, cunning, foxy, slick, sly, subtle, wily; defrauding, devious, furtive, slippery, sneaking, sneaky, trickish, tricky; insidious, perfidious, treacherousNear Antonyms conscientious, decent, ethical, honorable, just, scrupulous, upright; forthright, straightforwardAntonyms aboveboard, honest, straight

2 undertaken or done so as to escape being observed or known by others an underhanded attempt at infiltrating the other party's headquarters Synonyms backstairs, behind-the-scenes, clandestine, covert, furtive, hole-and-corner, hugger-mugger, hush-hush, private, privy, sneak, sneaking, sneaky, stealth, stealthy, surreptitious, undercover, underground, underhand, secretRelated Words back-channel, closed-door, off-the-books, off-the-record; classified, confidential, restricted, top secret, undisclosed; concealed, hidden, secreted, subterranean, unadvertised, unexposedNear Antonyms acknowledged, avowed; aboveboard, straightforward, unconcealed, undisguised; unclassified, unrestricted; clear, evident, manifest, obvious, patent, plainAntonyms open, overt, public