Synonyms: secret, undercover, underground, surreptitious, hole-and-corner, hugger-mugger, hush-hush, clandestine, cloak-and-dagger
Definition: conducted with or marked by hidden aims or methods
Usage: clandestine intelligence operations; cloak-and-dagger activities behind enemy lines; hole-and-corner intrigue; secret missions; a secret agent; secret sales of arms; surreptitious mobilization of troops; an undercover investigation; underground resistance
Similar words: covert
Definition: secret or hidden; not openly practiced or engaged in or shown or avowed
Usage: covert actions by the CIA; covert funding for the rebels
Synonyms: stealthy, surreptitious, sneak, sneaky, furtive
Definition: marked by quiet and caution and secrecy; taking pains to avoid being observed
Usage: a furtive manner; a sneak attack; stealthy footsteps; a surreptitious glance at his watch
Similar words: concealed
Definition: hidden on any grounds for any motive
Usage: a concealed weapon; a concealed compartment in his briefcase