Any great circle of the celestial sphere passing through the zenith and the nadir and perpendicular to the horizon.
Webster's New World
Other Word Forms of Vertical Circle
Vertical Circle Sentence Examples
Attached to the cross-arm which carries the microscopes used to observe the ends of the dipping needle is a clamp, which will hold the needle b in such a way that its plane is parallel to the vertical circle and its axis is at right angles to the line joining the two microscopes.
A vertical circle passing through the sun may also be seen.
Reflection from an excess of horizontal prisms gives rise to a vertical circle passing through the sun.
To the telescope the vertical circle for reading angles in This word has been a puzzle to etymologists.
The instrument is similar to that described above, except that the vertical circle is not continuous, but is formed of two arcs.