Definition of mean solar time in English:

mean solar time

noun

Astronomy
  • [mass noun] Time as calculated by the motion of the mean sun (such as is shown by an ordinary clock).

    • ‘The mean solar time on the Greenwich Meridian of longitude, was defined to pass through the Airy Transit Circle at Greenwich in England and was adopted internationally as the zero of longitude at a conference in Washington in 1884.’
    • ‘The tropical, or solar, year is measured relative to the sun and is the time between successive vernal equinoxes (365 days, 5 hr, 48 min, 46 sec of mean solar time).’