1. The path of a celestial body or an artificial satellite as it revolves around another body; one complete revolution of such a body.
2. The curved path, usually elliptical, described by a planet, satellite, spaceship, etc., around a celestial body, as the sun.
3. The path of a body in a field of force surrounding another body; for example, the movement of an atomic electron in relation to a nucleus.
4. A range of activity, experience, or knowledge; a range of control or influence.
5. The usual course of one's life or range of one's activities.
6. The sphere of power or influence, as of a nation or person: a small nation in the Russian orbit.
7. In physics, the path traced by an electron revolving around the nucleus of an atom.
8. An orb or sphere.
9. In zoology, the part surrounding the eye of a bird or insect.
10. Either of two bony cavities in the skull containing an eye and its external structures; an eye socket.

The path of an electron or the path described by an electron as it circulates around around the nucleus of an atom.