![vertical circle vertical circle](https://www.tekportal.net/wp-content/uploads/2018/11/vertical-circle.gif)
noun Astronomy.
- a great circle on the celestial sphere passing through the zenith.
noun
- astronomy a great circle on the celestial sphere passing through the zenith and perpendicular to the horizon
- A great circle on the celestial sphere that passes through the zenith and the nadir and thus is perpendicular to the horizon.