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