back stairs
backstair
covert
back-door
clandestine
feline
furtive
hidlings
hole-and-corner
hugger-mugger
privy
quiet
shifty
skulking
slinking
slinky
sly
sneaking
sneaky
stealthy
surreptitious
under-the-counter
under-the-table
undercover
underground
underhand
underhanded
unobtrusive
staircase
stairway
front stairs