[1] : The Collaborative International Dictionary of English v.0.48

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.
      1913 webster

   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.
      1913 webster

   3. an arch. obs.
      1913 webster

            statues and trophies, and triumphal arcs. --milton.
      1913 webster

   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.
      1913 webster

   electric arc, voltaic arc. see under voltaic.
      1913 webster
see also:
arch electric arc voltaic arc voltaic 

[2] : WordNet (r) 2.0

electric arc
     n : electrical conduction through a gas in an applied electric
         field syn: discharge, spark, arc, electric
         discharge
see also:
discharge spark arc electric discharge 

Arc >> A Words
Arc, definition of term: Arc
arc_pag1.html

Arc Light >> A Words
Arc Light, definition of term: Arc Light
arc+light_pag1.html