Source : Webster's Revised Unabridged Dictionary (1913)

Duel \Du"el\, n. [It. duello, fr. L. duellum, orig., a contest
   between two, which passed into the common form bellum war,
   fr. duo two: cf. F. duel. See {Bellicose}, {Two}, and cf.
   {Duello}.]
   A combat between two persons, fought with deadly weapons, by
   agreement. It usually arises from an injury done or an
   affront given by one to the other.

   {Trial by duel} (Old Law), a combat between two persons for
      proving a cause; trial by battel.

Duel \Du"el\, v. i. & t.
   To fight in single combat. [Obs.]

Source : WordNet®

duel
     n 1: a prearranged fight with deadly weapons by two people
          (accompanied by seconds) in order to settle a quarrel
          over a point of honor [syn: {affaire d'honneur}]
     2: any struggle between two skillful opponents (individuals or
        groups)
     v : fight a duel, as over one's honor or a woman; "In the 19th
         century, men often dueled over small matters"
     [also: {duelling}, {duelled}]

Source : Free On-Line Dictionary of Computing

DUEL
     
        A front end to {gdb} by Michael Golan .
        DUEL implements a language designed for debugging {C}
        programs.  It mainly features efficient ways to select and
        display data items.  It is normally linked into the gdb
        executable, but could stand alone.  It interprets a subset of
        {C} in addition to its own language.
     
        Version 1.10.
     
        {(ftp://ftp.cs.princeton.edu/duel/)}.
     
        (1993-03-20)