Definitions

1. adjective

relating to or measured from the stars; especially, relating to the fixed stars, as distinguished from the planets.

“The astronomer studied the sidereal time of the celestial body.”

2. noun

a star; especially, a star used as a reference point for measuring the position of other celestial bodies.

“The sidereal was used as a reference point in the ancient star chart.”

3. noun

time based on the Earth’s rotation relative to the fixed stars; as opposed to solar time.

“The sidereal time was used for navigation purposes in the 19th century.”