1
- chiefly Brit. a box attached to an outside wall, or a slot in the door of a house or other building, into which mail is delivered〈主英〉邮政信箱。
1.1
letterbox
usu. as modifier a format for presenting widescreen films on a standard television screen in which the image is displayed in approximately its original proportions across the middle of the screen, leaving horizontal black bands above and below信箱式放映（宽银幕电影在标准电视屏幕上放映, 画面基本以原比例显示, 上下各有黑边）：this uncut version is presented in letterbox format.
这个未剪辑的版本以信箱式放映。
(letterbox)with obj.
- record (a widescreen film) on to video in letterbox format.将（宽银幕电影）以信箱格式转成录像。