arc /ɑːk $ ɑːrk/ BrE AmE noun [countable]
[ Date: 1300-1400 ; Language: Old French ; Origin: Latin arcus 'bow, arch, arc' ]
1 . a curved shape or line:
the arc of a rainbow
2 . part of a curved line or a circle:
The Sun moves across the sky in an arc.
3 . a flash of light formed by the flow of electricity between two points
—arc verb [intransitive]