/ ˈɔːbɪtl; NAmE ˈɔːrb-/ adjective , noun
■ adjective [ only before noun ]
1.
connected with the orbit of a planet or object in space
2.
( BrE ) ( of a road ) built around the edge of a town or city to reduce the amount of traffic travelling through the centre
■ noun
( BrE ) a very large ring road , especially if it is a motorway :
the M25 London orbital
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WORD ORIGIN
mid 16th cent. (referring to the eye socket): probably from medieval Latin orbitalis , from Latin orbita course, track (in medieval Latin eye socket), feminine of orbitus circular, from orbis ring.