Arch — Defs

01 n. Any part of a curved line.

1.
Any part of a curved line.(Geom.)
2.
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.(Arch.)
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.

Phrases & compounds

Triumphal arch — a monumental structure resembling an arched gateway, with one or more passages, erected to commemorate a triumph.

02 v. t. To cover with an arch or arches.

imp. & p. p. Arched; p. pr. & vb. n. Arching

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.

03 v. i. To form into an arch; to curve.

04 a. Chief; eminent; greatest; principal.

1.
Chief; eminent; greatest; principal.
“The most arch act of piteous massacre.” — Shak.
2.
Cunning or sly; sportively mischievous; roguish; as, an arch look, word, lad.
“[He] spoke his request with so arch a leer.” — Tatler.

05 n. A chief.