Astronomy. the time interval between two successive transits by the sun of the meridian directly opposite that of the observer; the 24-hour interval from one midnight to the following midnight.
2.
Law. the period of time from sunrise to sunset.
Origin
1755-65
Examples from the web for solar day
The company also manufactures solar day-lighting products and distributes solar light tubes.
There are secular variations in this period, but they are much more predictable than the changes in the length of the solar day.
British Dictionary definitions for solar day
solar day
noun
1.
the period of time during which the earth makes one complete revolution on its axis relative to the sun See day (sense 6)