The colloquial term used to describe a video program where the original scene has a larger (wider) aspect ratio than the TV screen and is zoomed out (shrunk) so that the entire width fits in the screen. An inescapable consequence is that there is unused screen area and wasted scan lines at the top and bottom. The term came about because viewers had the impression they were looking through a mail slot in a door or out of the slot of a gigantic mailbox. Not all movies are offered on video this way because the public continues to demand editions where the entire screen is filled. Also the vertical resolution of subject matter in letterbox editions is less compared with full screen pan and scan editions of movies. Although I have not seen any movies prepared in the following way it might have been interesting to gauge the public's reaction if instead of black bars, an image of a theater proscenium curtain appeared above and below the letterboxed picture.

This definition is in context to Television. See more contextual defintions for Letterbox.