What is a meridian in the solar system?

Answer 1

I can not find any reference to a Meridian in the Solar System.

In astronomy, there is the Earth's meridian. That's a "great circle" on the "celestial sphere". It passes through the "celestial poles" and also through the "zenith" at the observer's location.

Answer 2

In the solar system, a meridian is an imaginary line that runs from the north pole to the south pole of a planet or celestial body, passing through its equator. It is used as a reference point for navigation and determining locations on the surface of planets and moons.