Arc (&unr_;), 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.
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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.
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3. An arch. [Obs.]
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Statues and trophies, and triumphal arcs. Milton.
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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.
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Electric arc, Voltaic arc. See under Voltaic.
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