Closed session of the United States Congress
In the Congress of the United States, a closed session (formally a session with closed doors) is a parliamentary procedure for the Senate or the House of Representatives to discuss matters requiring secrecy. The discussions which take place in a closed session are subject to confidentiality rules and are similar to an executive session, which itself can be open or closed.
Source: Wikipedia — Closed session of the United States Congress (CC BY-SA 4.0)