A structure that appears as an arc or incomplete ring around a planet, especially Neptune, generally representing part of a complete ring in which the rest of the ring is faint or invisible.
Origin
1980s; earliest use found in Science.
Definition of ring arc in US English:
ring arc
noun
Astronomy
A structure that appears as an arc or incomplete ring around a planet, especially Neptune, generally representing part of a complete ring in which the rest of the ring is faint or invisible.