Arch \Arch\, n. [F. arche, fr. LL. arca, for arcus. See Arc.]

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

2. (Arch.)
   (a) 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.'' --Milton.

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

Source: Webster's Revised Unabridged Dictionary (1913)
 

Arch \Arch\, n. [See Arch-, pref.]

A chief. [Obs.]

My worthy arch and patron comes to-night. --Shak.

Source: Webster's Revised Unabridged Dictionary (1913)
 

-arch \-arch\ [Gr. 'archo`s chief, commander, 'a`rchein to rule. See Arch, a.]

A suffix meaning a ruler, as in monarch (a sole ruler).

Source: Webster's Revised Unabridged Dictionary (1913)
 

Arch \Arch\, v. t. [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.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Arch \Arch\, v. i. To form into an arch; to curve.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Arch- \Arch-\ (["a]rch-, except in archangel and one or two other words). [L. arch-, Gr. ?. See Arch-.]

A prefix signifying chief, as in archbuilder, archfiend.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Arch \Arch\ (["a]rch), a. [See Arch-, pref.]

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.

Source: Webster's Revised Unabridged Dictionary (1913)