furtive
1. [ adjective ] marked by quiet and caution and secrecy; taking pains to avoid being observed
Synonyms: stealthy skulking sneaky sneak surreptitious lurking
Examples:

"a furtive manner" "a lurking prowler" "a sneak attack" "stealthy footsteps" "a surreptitious glance at his watch" "someone skulking in the shadows"

Related terms: concealed
2. [ adjective ] secret and sly or sordid
Synonyms: backstairs backstair
Examples:

"backstairs gossip" "his low backstairs cunning"- A.L.Guerard "backstairs intimacies" "furtive behavior"

Related terms: covert
Similar spelling:   furtively