arcus

Cum hoc arcus ejus extenditur, et primo sagittam in partem contrariam transmittit, et unum interficit.
The Fair Maid of Perth|Sir Walter Scott
The frustules are curved or arcuate (arcus, a bow) in the side view, oblong and narrowed at the ends in the front view.
An Elementary Text-book of the Microscope|John William Griffith
Du Cange gives arcus sellae equestris as one of the meanings of circus.
The Latin & Irish Lives of Ciaran|Anonymous
They are called arcus horarum inequalium, as they shew the 'houres inequales.'
Chaucer's Works, Volume 3 (of 7)|Geoffrey Chaucer

Its claim, as the parent of projectile implements, is recognized in the common etymology of arcus, arcualia—artillery.
Lippincott's Magazine of Popular Literature and Science Vol. XV., No. 85. January, 1875.|Various

Medical definitions for arcus

arcus

[ är′kəs ]

n. pl. arcus

A structure resembling a bent bow or an arch.