See also: top-secret
- (military) Information classified at the highest level of sensitivity by a government, based on an assessment that it would cause exceptionally grave damage to national security if disclosed.
- NSA's report on the Liberty incident was originally classified top secret.
- A level of security clearance needed to access such information.
- (figuratively) Pertaining to any especially sensitive closed-room activities.
- Steve Jobs set up a top secret team to design the Macintosh.
information classified at the highest level