underhand

1 given to or marked by cheating and deception willing to stoop to underhand methods in order to win Synonyms bent [chiefly British], crooked, deceptive, double-dealing, duplicitous, fast, fraudulent, guileful, rogue, shady, sharp, shifty, dishonest, underhandedRelated 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 the congressman's underhand attempt to slip several pork barrel items into the bill 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, secret, underhandedRelated 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