(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.
... like staring straight into the focus of a ten thousand candle-power electric arc lamp. It was so intolerable that Redgrave closed the lower shutters, and meanwhile he found that the Astronef had ceased to descend. He shut off more of the R. Force, but it produced no effect. ... — A Honeymoon in Space • George Griffith
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