archn.[F. arche, fr. LL. arca, for arcus. See Arc.]1. (Geom.) Any part of a curved line.()2. (Arch.) 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.()()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.(Milton.)Triumphal arch, a monumental structure resembling an arched gateway, with one or more passages, erected to commemorate a triumph.()v. t.1. To cover with an arch or arches.()2. To form or bend into the shape of an arch.()The horse arched his neck. (Charlesworth.)v. i. To form into an arch; to curve.()()