تعريف sidereal day في الإنجليزية الإنجليزية القاموس.
the time for one complete rotation of the earth relative to a particular star, about 4 minutes shorter than a mean solar day
The time required for a complete rotation of the earth in reference to any star or to the vernal equinox at the meridian, equal to 23 hours, 56 minutes, 4.09 seconds in units of mean solar time