stealthy (adj.)

• acute
• arch
• artful
• astute
• backstairs
• cagey
• canny
• catty
• clandestine
• clever
• covert
• crafty
• cunning
• cute
• deceitful
• deep
• deep-laid
• designing
• diplomatic
• feline
• foxy
• furtive
• guileful
• hole-and-corner
• hugger-mugger
• hush-hush
• ingenious
• insidious
• inventive
• knowing
• noiseless
• pawky
• politic
• privy
• quiet
• ready
• resourceful
• scheming
• secret
• secretive
• serpentine
• sharp
• shifty
• shrewd
• silent
• slick
• slippery
• sly
• smooth
• snaky
• sneak
• sneaking
• sneaky
• sophistical
• strategic
• subtle
• supple
• surreptitious
• tactical
• tricksy
• tricky
• under-the-counter
• under-the-table
• undercover
• underground
• underhand
• underhanded
• unobtrusive
• vulpine
• wary
• wily