classified
Sorted into classes or categories.
Other meanings
Formally assigned by a government to one of several levels of sensitivity, usually (in English) top secret, secret, confidential, and, in some countries, restricted; thereby making disclosure to unauthorized persons illegal.
“We do not discuss specific interrogation techniques because they are classified information.”
Not meant to be disclosed by a person or organization.
“I won't say who I'm going to the prom with; that's classified.”
Where this comes from
This definition is adapted from “classified” on Wiktionary, by its contributors, published under CC BY-SA 4.0. This page is published under the same licence.