Far out, man. I mean really far out — as in related to the distant stars of the universe. That's what sidereal means.

Pronunciation: /saɪ'dɪrɪəl/
English Description: of or relating to the stars or constellations
Synonyms: civil
Chinese Translation: 恒星的(heng2 xing1 de)
Spanish Translation: sidéreo
ORIGIN: Sidereal is an adjective that first popped up in the 17th century, and stems from the Latin word sidereus, which means "star." Anything that's sidereal has something to do with stars and constellations. And if you measure the days and weeks by the movement of the stars across the sky, that's called sidereal astronomy or sidereal time. But if you've got someplace to be, you'd be better off with a good calendar and a wristwatch.

EXAMPLE SENTENCE:

A sidereal day is approximately 23 hours, 56 minutes and 4.1 seconds.
The length of this sidereal solar year was determined in the following manner.

*New word description, story and part of "EXAMPLE SENTENCE" are cited in Vocabulary.com