Definitions for **"Mean sun"**

An imaginary average solar motion that yields a 24-hour day. Clocks and wristwatches measure time with respect to the mean Sun, not actual solar motion.

a theoretical sun that moves along the celestial equator at a constant speed and completes its annual course in the same amount of time the real sun takes at variable speeds

Fictitious sun projected to move along the equinoctial at a constant rate, and completing its circle in one solar year.