letter-box slot矩形翼缝
letter-box inlet矩形进气口
letter-box company信箱公司
letter-box x邮箱
letter- box信筒
Medium-sized letter-box中型信盒
letter-box letter-folders信箱
dead-letter box死信箱
N-COUNT（可数名词） A letterbox is a rectangular hole in a door or a small box at the entrance to a building into which letters and small packages are delivered. 信箱 [英国英语]
The next day there was a letter in her letterbox.
第二天她的信箱里有封信。
ADJ（形容词） 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. (电视或电脑上的影像) 宽屏带黑边的