| adjective | marked by quiet and caution and secrecy; taking pains to avoid being observed “a furtive manner” |
| adjective | conducted with or marked by hidden aims or methods “clandestine intelligence operations” |
| furtiveness | noun | a disposition to be sly and stealthy and to do things surreptitiously |
| sneak | noun | a person who is regarded as underhanded and furtive and contemptible |
| sneakiness | noun | a disposition to be sly and stealthy and to do things surreptitiously |
| stealth | noun | avoiding detection by moving carefully |
| stealthiness | noun | a disposition to be sly and stealthy and to do things surreptitiously |
| underground | noun | a secret group organized to overthrow a government or occupation force |