• adjective a second or third system, instrument or computer disk available to be used if the first one fails


  • noun the providing of help
  • noun a copy of a file or data or disk made as a security precaution.
  • noun the process of making a copy of a file or data or disk as a security precaution
  • noun
    (written as BACKUP)
    a command to backup data from a hard disk onto floppy disks or a tape drive


  • That part of a masonry wall behind the exterior facing.
  • Any substance placed into a joint to seal the joint and reduce its depth, and/or to inhibit sagging of the sealant.
  • overflow due to blockage in a piping system.
  • Supporting documents for an estimate or schedule including detailed calculations, descriptions of data sources, and comments on the quality of the data.


  • A duplicate copy of computer data available on an additional storage medium such as a floppy disk, to be used in case of need. Also called backup copy.
  • Additional resources which are available to substitute those which fail. For example, a diode replacing another which has failed.
  • Additional resources which serve to supplement others, such as backup battery.

Information & Library Science

  • noun a duplicate copy of a file on a computer

Media Studies

  • noun a copy of saved data that can be used if the original is lost, or a second source of energy or facilities that may be used if the first source fails


  • noun an additional assistance or resources available in the event of difficulty or failure


  • noun a delay in a flight caused by too much air traffic