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
3. An arch. [Obs.]
Statues and trophies, and triumphal arcs.
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
Electric arc, Voltaic arc. See
Arc (ärk), v. i. [imp. &
p. p. Arcked (ärkt); p. pr. & vb.
n. Arcking.] (Elec.) To form a voltaic
arc, as an electrical current in a broken or disconnected