Historical the part of a circle that is the apparent path of a heavenly body above and below the horizon
a bowlike curved line or object
Elec. the band of sparks or incandescent light formed when an electric discharge is conducted from one electrode or conducting surface to another, characterized by relatively high current and low potential difference between electrodes
Geom.
any part of a curve, esp. of a circle
the angular measurement of this
adjective
designating an inverse trigonometric function: arc sine x is an angle whose sine is x