information known only to a special group; "the secret of Cajun cooking"
something that should remain hidden from others (especially information that is not to be passed on); "the combination to the safe was a secret"; "he tried to keep his drinking a secret"
the next to highest level of official classification for documents
not expressed; "secret (or private) thoughts"
indulging only covertly; "a secret alcoholic"
communicated covertly; "their secret signal was a wink"; "secret messages"
not open or public; kept private or not revealed; "a secret formula"; "secret ingredients"; "secret talks"
intelligence activities concerned with identifying and counteracting the threat to security posed by hostile intelligence organizations or by individuals engaged in espionage or sabotage or subversion or terrorism
happening or arising or located within some limits or especially surface; "internal organs"; "internal mechanism of a toy"; "internal party maneuvering"
occurring within an institution or community; "intragroup squabbling within the corporation"
away from the outer edge; "an inner lane"; "the inside lane"
relating to or being on the side closer to the center or within a defined space; "he reached into his inside jacket pocket"; "inside out"; "an inside pitch is between home plate and the batter"
confined to an exclusive group; "privy to inner knowledge"; "inside information"; "privileged information"
difficult to penetrate; incomprehensible to one of ordinary understanding or knowledge; "the professor's lectures were so abstruse that students tended to avoid them"; "a deep metaphysical theory"; "some recondite problem in historiography"