Arch

1. n. Any curvature in the form of an arch; as, the arch of the aorta.
2. n. Any part of a curved line.
3. n. 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.
4. n. 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.
5. n. Any place covered by an arch; an archway; as, to pass into the arch of a bridge.

The word meanings were obtained from OPTED(The Online Plain Text English Dictionary), which is based on “The Project Gutenberg Etext of Webster’s Unabridged Dictionary” which is in turn based on the 1913 US Webster’s Unabridged Dictionary (See Project Gutenburg), as a text file.