surreptitious
形容词 surreptitious:
marked by quiet and caution and secrecy; taking pains to avoid being observed
同义词:furtive, sneak, sneaky, stealthy
conducted with or marked by hidden aims or methods
同义词:clandestine, cloak-and-dagger, hole-and-corner, hugger-mugger, hush-hush, secret, undercover, underground