xanthineEnglishMerriam-Webster Dictionary>, fraudulent, insinuating, knavish, Machiavellian, oblique, serpentine, shady, shifty, slippery, sneaky, treacherous, underhand, underhanded, unscrupulousbackhanded, double-dealing, hypocritical, insincere, left-handed, mealy, mealymouthed, smooth-tongued, two-facedcircuitous, circular, roundaboutclandestine, concealed, covert, furtive, hugger-mugger, secret, stealthy, surreptitious, undercovercalculating, plotting