clandestine

clandestine (http://definr.com/clandestine)

     adj : conducted with or marked by hidden aims or methods;
           "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" [syn: cloak-and-dagger, hole-and-corner(a),
            hugger-mugger, hush-hush, on the quiet(p), secret,
            surreptitious, undercover, underground]