(superl.) Done by stealth; accomplished clandestinely; unperceived; secret; furtive; sly.

Machiavellian Machiavellic acute arch artful astute back-door backstairs cagey canny catlike catty clandestine clever closet covert crafty cunning cute deceitful deep deep-laid designing diplomatic doggo feline foxy furtive guileful hidden out hidlings hole-and-corner hugger-mugger hush-hush in ambush in hiding in the wings ingenious insidious inventive knowing lurking noiseless on tiptoe pawky politic privy prowling pussyfoot pussyfooted quiet ready resourceful scheming secret secretive serpentine sharp shifty shrewd silent skulking slick slinking slinky slippery sly smooth snaky sneak sneaking sneaky sophistical stealing stealthful strategic subtile subtle supple surreptitious tactical trickish tricksy tricky under cover under-the-counter under-the-table undercover underground underhand underhanded unobtrusive vulpine waiting concealed wary wily