asteroid [asteroids](astronomy: a naturally occurring solid object, which is smaller than a planet and is not a comet, that orbits a star) noun [UK: ˈæ.stə.rɔɪd] [US: ˈæ.stə.ˈrɔɪd]An asteroid exploded over Chelyabinsk in Russia. = En asteroid exploderade över Tjeljabinsk i Ryssland.