Subastral refers to something that is below or beneath the stars. Therefore, the antonyms for this word would be "suprastral" or "celestial," which mean above or beyond the stars, respectively. Other antonyms for subastral could be "terrestrial, earthly, or mundane," which mean of or pertaining to the Earth or the material world. In contrast, "ethereal, heavenly, or divine" would be considered as synonyms for suprastral and celestial, as they denote a spiritual or godly nature. The antonyms for subastral can be useful to describe the location, quality, or essence of a celestial object or phenomena.