1 N-COUNT (门上的)信件投递孔;(建筑物入口处的)信箱 A
letterbox 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.
(门上的)信件投递孔;(建筑物入口处的)信箱 [mainly British] in AM, usually use 美国英语通常用 mailbox
2 ADJ (电视或计算机显示)信箱格式的,上下黑边的,宽屏的 If something is displayed on a television or computer screen in
letterbox format, it is displayed across the middle of the screen with dark bands at the top and bottom of the screen.
(电视或计算机显示)信箱格式的,上下黑边的,宽屏的