also back-room, back room
1.
A ~ is a room that is situated at the back of a building, especially a private room.
...the ~ of the officers’ club.
N-COUNT
2.
You can use ~ to refer to people in an organization who do important work but are not seen or known about by the public. You can also use ~ to refer to a place where such people work.
Public scrutiny had brought civil servants out from the ~ and into the spotlight.
...Mr Smith’s ~ staff.
N-COUNT
3.
If you refer to a deal made by someone such as a politician as a ~ deal, you disapprove of it because it has been made in a secret, dishonest way.
They have been calling the Presidency decision a ~ deal.
ADJ: ADJ n disapproval