official secret
noun [ C ] UK uk/əˌfɪʃ.əl ˈsiː.krət/ us/əˌfɪʃ.əl ˈsiː.krət/
国家机密，官方机密
a piece of information that is known only by the government and its employees
She was accused of leaking (= telling) official secrets to the newspapers. 她被指控把国家机密泄露给报界。