Source : Webster's Revised Unabridged Dictionary (1913)

Background \Back"ground`\, n. [Back, a. + ground.]
   1. Ground in the rear or behind, or in the distance, as
      opposed to the foreground, or the ground in front.

   2. (Paint.) The space which is behind and subordinate to a
      portrait or group of figures.

   Note: The distance in a picture is usually divided into
         foreground, middle distance, and background.
         --Fairholt.

   3. Anything behind, serving as a foil; as, the statue had a
      background of red hangings.

   4. A place in obscurity or retirement, or out of sight.

            I fancy there was a background of grinding and
            waiting before Miss Torry could produce this highly
            finished . . . performance.           --Mrs.
                                                  Alexander.

            A husband somewhere in the background. --Thackeray.

Source : WordNet®

background
     n 1: a person's social heritage: previous experience or training;
          "he is a lawyer with a sports background"
     2: the part of a scene (or picture) that lies behind objects in
        the foreground; "he posed her against a background of
        rolling hills" [syn: {ground}]
     3: information that is essential to understanding a situation
        or problem; "the embassy filled him in on the background
        of the incident" [syn: {background knowledge}]
     4: extraneous signals that can be confused with the phenomenon
        to be observed or measured; "they got a bad connection and
        could hardly hear one another over the background signals"
        [syn: {background signal}]
     5: relatively unimportant or inconspicuous accompanying
        situation; "when the rain came he could hear the sound of
        thunder in the background"
     6: the state of the environment in which a situation exists;
        "you can't do that in a university setting" [syn: {setting},
         {scope}]
     7: (computer science) the area of the screen in graphical user
        interfaces against which icons and windows appear [syn: {desktop},
         {screen background}]
     8: scenery hung at back of stage [syn: {backdrop}, {backcloth}]

background
     v : understate the importance or quality of; "he played down his
         royal ancestry" [syn: {play down}, {downplay}] [ant: {foreground},
          {foreground}]

Source : Free On-Line Dictionary of Computing

background
     
        1.  A task running in the background (a
        background task) is detached from the terminal where it was
        started (and often running at a lower priority); opposite of
        {foreground}.  This means that the task's input and output
        must be from/to files (or other processes).
     
        Nowadays this term is primarily associated with {Unix}, but it
        appears to have been first used in this sense on {OS/360}.
     
        Compare {amp off}, {batch}, {slopsucker}.
     
        2.  For a human to do a task "in the background" is to
        do it whenever {foreground} matters are not claiming your
        undivided attention, and "to background" something means to
        relegate it to a lower priority.  "For now, we'll just print a
        list of nodes and links; I'm working on the graph-printing
        problem in the background."  Note that this implies ongoing
        activity but at a reduced level or in spare time, in contrast
        to mainstream "back burner" (which connotes benign neglect
        until some future resumption of activity).  Some people prefer
        to use the term for processing that they have queued up for
        their unconscious minds (often a fruitful tack to take upon
        encountering an obstacle in creative work).
     
        (1996-05-28)