• noun a short coat with long sleeves worn with trousers or skirt


  • A covering, either of cloth or metal, applied to exposed heating pipes or ducts, to exposed or unexposed casing pipes, or over the insulation of such pipes.
  • A watertight outer housing around a pipe or vessel, the space between being occupied by a fluid for heating, cooling, or maintaining a specific temperature.
  • In wire and cable, the outer sheath or casing that protects the individual wires within from the elementsand provides additional insulation properties.


  • The outermost layer of a component, connector, cable, floppy disk, or the like, which provides protection and structural support. A jacket may also server to provide additional insulation, even when surrounding an insulator.

Information & Library Science

  • noun a paper or plastic cover for a book
  • verb to put a jacket on a book


  • noun a personal file, record; particularly a police file or prisoner’s dossier. A law enforcers’ term, from the jargon of office-workers.