artful, back-door, backstairs, calculating, chiseling, clandestine, collusive, conspiratorial, covert, covinous, crafty, cunning, deceitful, doggo, FALSE, falsehearted, feline, finagling, foxy, fraudulent, guileful, hidden, hidden out, hidlings, hole-and-corner, hugger-mugger, in ambush, in hiding, in the wings, indirect, insidious, lurking, on tiptoe, private, privy, prowling, pussyfoot, pussyfooted, quiet, scheming, secret, secretive, sharp, shifty, skulking, slinking, slinky, slippery, sly, sneaking, sneaky, stealing, stealthy, surreptitious, treacherous, trickish, tricky, two-faced, under cover, under the table, under-the-counter, under-the-table, undercover, underground, underhand, underhanded, unobtrusive, untrustworthy, waiting concealed, wily