surreptitious
adjective
1. marked by quiet and caution and secrecy; taking pains to avoid being observed
- a surreptitious glance at his watch
Similar word(s): concealed, furtive, sneak, sneaky, stealthy
2. conducted with or marked by hidden aims or methods
- surreptitious mobilization of troops
Similar word(s): covert, clandestine, secret, undercover, underground