behind closed doors

prep_phrase

(idiomatic) In private; in one's private life; lacking (normal) public disclosure, in camera. / (idiomatic, sports) Without public spectators.

They discussed the matter behind closed doors.

意味（1）

(idiomatic) In private; in one's private life; lacking (normal) public disclosure, in camera.

What you do with your girlfriend behind closed doors is none of my business.

意味（2）

(idiomatic, sports) Without public spectators.

Libya's opening home match in the World Cup qualifiers against Cameroon will be played at a neutral venue and behind closed doors, FIFA said on Friday. https://web.archive.org/web/20150611004158/http://in.reuters.com/article/2012/04/20/soccer-world-libya-idINDEE83J07G20120420