kept or hidden from knowledge or view
marked by the practice of discretion; secretive
archaic said of a person: discreet; keeping the lips sealed
Indeed, this counsellor is now most still, most secret, and most grave, who was in life a foolish prating knave — Shakespeare
conducted or operating in secret
secret negotiations
retired or secluded
revealed only to the initiated; esoteric
secret rites
containing information whose unauthorized disclosure could endanger national security