adjective: (military, government) Information classified at one of the highest levels of sensitivity by a government, based on an assessment that it would cause exceptionally grave damage to national security if disclosed.
adjective: A level of security clearance needed to access such information.
adjective: (figuratively) Pertaining to any especially sensitive closed-room activities.
noun: A secret that is classed as "top secret"; top-secret information.
noun: Used other than figuratively or idiomatically: see top, secret.
