1. [n]  electrical conduction through a gas in an applied electric field
2. [n]  a continuous portion of a circle
3. [n]  something curved in shape
4. [v]  form an arch

ARC is a 3 letter word that starts with A.

1. \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}.
   

2. \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.
   

1. advanced risc computing specification

2. 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.