Source : Webster's Revised Unabridged Dictionary (1913)

Arc \Arc\ ([aum]rk), v. i. [imp. & p. p. {Arcked} ([aum]rkt); p.
   pr. & vb. n. {Arcking}.] (Elec.)
   To form a voltaic arc, as an electrical current in a broken
   or disconnected circuit.

Arc \Arc\, n. [F. arc, L. arcus bow, arc. See {Arch}, n.]
   1. (Geom.) A portion of a curved line; as, the arc of a
      circle or of an ellipse.

   2. A curvature in the shape of a circular arc or an arch; as,
      the colored arc (the rainbow); the arc of Hadley's
      quadrant.

   3. An arch. [Obs.]

            Statues and trophies, and triumphal arcs. --Milton.

   4. The apparent arc described, above or below the horizon, by
      the sun or other celestial body. The diurnal arc is
      described during the daytime, the nocturnal arc during the
      night.

   {Electric arc}, {Voltaic arc}. See under {Voltaic}.

Source : WordNet®

arc
     n 1: electrical conduction through a gas in an applied electric
          field [syn: {discharge}, {spark}, {electric arc}, {electric
          discharge}]
     2: a continuous portion of a circle
     3: something curved in shape [syn: {bow}]
     [also: {arcking}, {arcked}]

arc
     v : form an arch or curve; "her back arches"; "her hips curve
         nicely" [syn: {arch}, {curve}]
     [also: {arcking}, {arcked}]

Source : Free On-Line Dictionary of Computing

arc
     
        1.  An old {archive} format for {IBM PC}.
        The format is now so obscure that it is only likely to be
        supported by jack-of-all-trades decompression programs such as
        {WINZIP}.
     
        2.  An {edge} in a {tree}.  "{branch}" is a
        generally more common synonym.
     
        (1998-12-29)

ARC
     
        {Advanced RISC Computing Specification}