also letter box
(~es)
1.
A ~ is a rectangular hole in a door or a small box at the entrance to a building into which letters and small parcels are delivered. Compare post box . (mainly BRIT; in AM, usually use mailbox )
N-COUNT
2.
If something is displayed on a television or computer screen in ~ format, it is displayed across the middle of the screen with dark bands at the top and bottom of the screen.
ADJ