Time told by a fictitious sun in which the earth is neither tilted on its axis nor moving about the sun in an elliptical orbit. This is the time indicated by a standard clock or wrist watch.

a measure of time based conceptually on the diurnal motion of the fictitious mean sun, under the assumption that the Earth's rate of rotation is constant.

hour of day as determined by the apparent angular motion of the sun across the sky, with solar noon as the reference point for 12 o'clock  wahre Ortszeit

(astronomy) time based on the motion of the mean sun (an imaginary sun moving uniformly along the celestial equator)

Time based on an imaginary "mean Sun". See the tutorial on Time.