1) Backstair 2) Backstairs 3) Clandestine 4) Covert 5) Crafty 6) Guilty 7) Ratlike 8) Secret 9) Shifty 10) Skulking 11) Sly 12) Sneak 13) Sneaky 14) Stealthy 15) Surreptitious 1) Cautious 2) Characterised by stealth 3) Clandestine 4) Concealed 5) Covert 6) Crafty 7) French word used in English 8) Lurking 9) Quiet 10) Secret 11) Secret and sly or sordid 12) Silent 13) Skulking 14) Sneak 15) Sneaky 16) Stealthy 17) Stealthy; sneaky 18) Surreptitious 19) Underhand 
• (a.) Stolen; obtained or characterized by stealth; sly; secret; stealthy; as, a furtive look.
Fur'tive adjective [ Latin furtivus , from furtum theft, from fur thief, akin to ferre to bear: confer French furtif . See Fertile .] Stolen; obtained or characterized by stealth; sly; secret; stealthy; as, a furtive look. Prior. « A hasty and f...
[adj] - marked by quiet and caution and secrecy
sneak(a) adjective 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`
taken, done, used, etc., surreptitiously or by stealth; secret: a furtive glance. · sly; shifty: a furtive manner.
[Literary terms] marked by quiet and caution and secrecy[SAT terms] secret and sly or sordid[Lexical terms] secret and sly or sordid