Usually a curved member made up of separate wedge-shaped solids, with the joints between them disposed in the direction of the radii of the curve; used to support the wall or other weight above an opening. In this sense arches are segmental, round (i. e., semicircular), or pointed.
(b)
A flat arch is a member constructed of stones cut into wedges or other shapes so as to support each other without rising in a curve. Note: Scientifically considered, the arch is a means of spanning an opening by resolving vertical pressure into horizontal or diagonal thrust.
3.
Any place covered by an arch; an archway; as, to pass into the arch of a bridge.
4.
Any curvature in the form of an arch; as, the arch of the aorta. "Colors of the showery arch."
Triumphal arch, a monumental structure resembling an arched gateway, with one or more passages, erected to commemorate a triumph.
... without. This sledge was followed by a retinue of two thousand others. Every person, in all the sledges, was dressed in fancy costume, and masked. When two miles from the city, the train passed beneath a triumphal arch illuminated with all conceivable splendor. At the distance of every mile, some grand structure appeared in a blaze of light, a pyramid, or a temple, or colonnades, or the most brilliant displays of fireworks. Opposite each of these structures ball rooms had been reared, which were crowded ... — The Empire of Russia • John S. C. Abbott
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