Definition of "letterbox"

letterbox

noun
plural letterboxes
1. (chiefly UK) A box into which mail is put.
  1. A collection point for mail intended for onward delivery, a secure box or receptacle for this purpose.
  2. A delivery point for mail, a box, compartment or slot for this purpose.
2. A hidden container that holds a logbook and rubber stamp, found by following clues as a form of recreation.
3. (mountaineering) A rectangular hole or slot.
  Quotations
  His strength was running out fast: one more good letterbox was all that he could conceive himself able to make. He made it, hacking away with slow, painful strokes, his axe-handle slippery with his sweat.
  1954, Daniel Talbot, A Treasury of Mountaineering Stories, page 239
adjective
not comparable
1. (film) Transferred to home video formats while preserving the original aspect ratio, having black bars above and below the picture area.
verb
third-person singular simple present letterboxes, present participle letterboxing, simple past and past participle letterboxed
1. (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.
2. To hunt for letterboxes (containers with logbook and rubber stamp) by following clues.