"furtive" in the adjective sense
1. furtive, sneak, sneaky, stealthy, surreptitious
marked by quiet and caution and secrecy taking pains to avoid being observed
"a furtive manner"
"a sneak attack"
"stealthy footsteps"
"a surreptitious glance at his watch"
2. backstair, backstairs, furtive
secret and sly or sordid
"backstairs gossip"
"his low backstairs cunning"- A.L.Guerard
"backstairs intimacies"
"furtive behavior"
Source: WordNet® (An amazing lexical database of English)
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