(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."
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.
... see his infant dynamo, the first of its kind, developed into a machine not only sufficiently powerful to maintain electric arc lights, but also into a form sufficiently practicable to be continuously engaged in producing such light, in one of the lighthouses on the English coast. Holmes produced such a machine in 1862, or some years before Faraday's ... — Beacon Lights of History, Volume XIV • John Lord
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