Sideral is a word that relates to the stars or the universe. It is often used to describe things that are astronomical or other-worldly. Some synonyms for the word sideral include celestial, astral, cosmic, galactic, and stellar. The word celestial is often used to describe heavenly bodies like stars and planets, while astral is more commonly used to describe the mystical or ethereal aspects of the universe. Cosmic suggests something that is of vast scope or magnitude, while galactic is used to describe things that are associated with galaxies. Lastly, stellar is a term used to describe things that are related to stars, such as their brightness or uniqueness.