Another term for a widescreen DVD. A letterbox movie fills the entire screen of a widescreen HDTV. When you watch a letterbox movie on a regular TV screen, black bars are visible above and below the picture.
Because some images, such as wide-screen movies, do not fill a TV screen, black bars are placed above and below the image to fill the unused space. This allows to movie to be shown in its native aspect rather than being adjusted to fit the screen. When bars are placed to the left and right sides of an image it is called windowbox.
Black bars across the top and bottom of a 4:3 TV screen, so that the image appears in a 16:9 ("Widescreen") aspect ratio.