2. To form or bend into the shape of an arch.

The horse arched his neck.

Charlesworth.

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

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Arch- (ärch-, except in archangel and one or two other words). [L. arch-, Gr. &?;. See Arch-.] A prefix signifying chief, as in archbuilder, archfiend.

Arch (ärch), a. [See Arch-, pref.] 1. Chief; eminent; greatest; principal.

The most arch act of piteous massacre.

Shak.