noun: A collection point for mail intended for onward delivery, a secure box or receptacle for this purpose.
noun: A delivery point for mail, a box, compartment or slot for this purpose.
noun: A hidden container that holds a logbook and rubber stamp, found by following clues as a form of recreation.
noun: (mountaineering) A rectangular hole or slot.
adjective: (film) Transferred to home video formats while preserving the original aspect ratio, having black bars above and below the picture area.
verb: (film) To transfer a widescreen motion picture to home video formats while preserving the original aspect ratio, with the placing of black bars above and below the picture area.
verb: To hunt for letterboxes (containers with logbook and rubber stamp) by following clues.
