[adj] marked by quiet and caution and secrecy; taking pains to avoid being observed; "a furtive manner"; "a lurking prowler"; "a sneak attack"; "stealthy footsteps"; "a surreptitious glance at his watch"; "someone skulking in the shadows"
[adj] marked by deception; "achieved success in business only by underhand methods"
Synonyms
concealed, corrupt, crooked, furtive, lurking, skulking, sneak(a), stealthy, surreptitious, underhand, underhanded