- a public or private mailbox.
- a technique for displaying a wide-screen film or landscape video on a narrower screen by reducing its size but retaining the aspect ratio, with black bands filling the screen above and below the picture (often used attributively):letterbox videos.
- to display (a film or video) by using the letterbox technique.
- a slot, usually covered with a hinged flap, through which letters, etc, are delivered to a building
- a private box into which letters, etc, are delivered
- a public box into which letters, etc, are put for collection and delivery
