A segment or part of a circle. A concave or hollow structure of stone or brick, supported by its own curve. It may be constructed of wood, and supported by the mechanism of the work. This species of structure is much used in bridges. A vault is properly a board arch.

The space between two piers of a bridge, when arched; or any place covered with an arch.

Any curvature, in form of an arch.

The vault of heaven, or sky. Triumphal arches are magnificent structures at the entrance of cities, erected to adorn a triumph and perpetuate the memory of the event.

To cover with an arch; to form with a curve; as to arch a gate.

To make an arch or arches; as, to arch beneath the sand.

Cunning; sly; shrewd; waggish; mischievous for sport; mirthful; as we say in popular language, roguish; as an arch lad.

Used also in composition. Chief; of the first class; principal; as, an arch deed. Shakespeare uses this word as a noun; “My worthy arch and patrons;” but the use is not authorized.