Top secret means of the highest level of official secrecy. Marked top secret.
It is a formal classification with rules about who may read it and where. Something top secret is defined as material whose release would cause exceptionally grave damage.
1adjectivetop secretOf the highest level of official secrecy.
“The file was top secret and released after fifty years.”
top secret is a quality.
Practised in Spying & Secrecy