cylinder vs letterbox

cylinder

noun
  • Any object in the form of a circular cylinder. 

  • A surface created by projecting a closed two-dimensional curve along an axis intersecting the plane of the curve. 

  • The part of a revolver that contains chambers for the cartridges. 

  • A container in the form of a cylinder with rounded ends for storing pressurized gas; a gas cylinder. 

  • An early form of phonograph recording, made on a wax cylinder. 

  • A cylindrical cavity or chamber in a mechanism, such as the counterpart to a piston found in a piston-driven engine. 

  • The corresponding tracks on a vertical arrangement of disks in a disk drive considered as a unit of data capacity. 

  • The space in which a piston travels inside a reciprocating engine or pump. 

  • A solid figure bounded by a cylinder and two parallel planes intersecting the cylinder. 

verb
  • To calender; to press (paper, etc.) between rollers to make it glossy. 

letterbox

noun
  • A rectangular hole or slot. 

  • A hidden container that holds a logbook and rubber stamp, found by following clues as a form of recreation. 

  • A delivery point for mail, a box, compartment or slot for this purpose. 

  • A collection point for mail intended for onward delivery, a secure box or receptacle for this purpose. 

verb
  • 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. 

  • To hunt for letterboxes (containers with logbook and rubber stamp) by following clues. 

adj
  • Transferred to home video formats while preserving the original aspect ratio, having black bars above and below the picture area. 

How often have the words cylinder and letterbox occurred in a corpus of books? (source: Google Ngram Viewer )