The Collaborative International Dictionary of English v.0.48:

Foreground \Fore"ground`\, n.
   On a painting, and sometimes in a bas-relief, mosaic picture,
   or the like, that part of the scene represented, which is
   nearest to the spectator, and therefore occupies the lowest
   part of the work of art itself. Cf. Distance, n., 6.
   [1913 Webster]

WordNet (r) 3.0 (2006):

foreground
    n 1: the part of a scene that is near the viewer
    2: (computer science) a window for an active application
    v 1: move into the foreground to make more visible or prominent;
         "The introduction highlighted the speaker's distinguished
         career in linguistics" [syn: foreground, highlight,
         spotlight, play up] [ant: background, downplay,
         play down]

Moby Thesaurus II by Grady Ward, 1.0:

53 Moby Thesaurus words for "foreground":
   anteriority, approach, approximation, bold front, brave face,
   brave front, closeness, confines, convergence, display, environs,
   facade, face, facet, facia, fore, forefront, forehand, foreland,
   forepart, forequarter, foreside, foreword, front, front elevation,
   front man, front matter, front page, front view, frontage, frontal,
   frontier, frontispiece, head, heading, immediacy,
   immediate foreground, lap, nearness, neighborhood, nighness,
   obverse, precinct, preface, prefix, priority, propinquity,
   proscenium, proximity, purlieus, vicinage, vicinity,
   window dressing



The Jargon File (version 4.4.7, 29 Dec 2003):

foreground
 vt.

    [Unix; common] To bring a task to the top of one's stack for immediate
    processing, and hackers often use it in this sense for non-computer tasks.
    ?If your presentation is due next week, I guess I'd better foreground
    writing up the design document.?

    Technically, on a timesharing system, a task executing in foreground is one
    able to accept input from and return output to the user; oppose background
    . Nowadays this term is primarily associated with Unix, but it appears
    first to have been used in this sense on OS/360. Normally, there is only
    one foreground task per terminal (or terminal window); having multiple
    processes simultaneously reading the keyboard is a good way to lose.


The Free On-line Dictionary of Computing (30 December 2018):

foreground

   (Unix) On a time-sharing system, a task executing in
   foreground is one able to accept input from and return output
   to the user in contrast to one running in the background.
   Nowadays this term is primarily associated with Unix, but it
   appears first to have been used in this sense on OS/360.
   Normally, there is only one foreground task per terminal (or
   terminal window).  Having multiple processes simultaneously
   reading the keyboard is confusing.

   [Jargon File]

   (1994-10-24)