ETYM Greek, starlike, starry; aster star + eidos form: cf. French astéroďde. Related to Aster.
Any of numerous small celestial bodies composed of rock and metal that move around the sun (mainly between the orbits of Mars and Jupiter); SYN. minor planet, planetoid.
Small planet revolving between Jupiter and Mars; planetoid; any starlike body.
Or minor planet; Any of many thousands of small bodies, composed of rock and iron, that orbit the Sun. Most lie in a belt between the orbits of Mars and Jupiter, and are thought to be fragments left over from the formation of the Solar System. About 100,000 may exist, but their total mass is only a few hundredths the mass of the Moon.
They include Ceres (the largest asteroid, 940 km/584 mi in diameter), Vesta (which has a light-colored surface, and is the brightest as seen from Earth), Eros, and Icarus. Some asteroids are in orbits that bring them close to Earth, and some, such as the Apollo asteroids, even cross Earth’s orbit; at least some of these may be remnants of former comets. One group, the Trojans, moves along the same orbit as Jupiter, 60ş ahead and behind the planet. One unusual asteroid, Chiron, orbits beyond Saturn. The first asteroid moon was observed by the space probe Galileo 1993 orbiting asteroid Ida. Bifurcated asteroids, first discovered in 1990, are in fact two chunks of rock that touch each other. It may be that at least 10% of asteroids approaching the Earth are bifurcated. The first asteroid was discovered by the Italian astronomer Giuseppe Piazzi at the Palermo Observatory, Sicily, 1 Jan 1801.

Shaped like a star; SYN. star-shaped.
1. Resembling a star
2. Of or resembling a starfish.