late 14c., from Latin centaurus, from Greek Kentauros, origin disputed. In early Greek literature they were a savage, horse-riding tribe from Thessaly; later they were monsters half horse, half man. The southern constellation of Centaurus is attested in English from 1550s but was known by that name to the Romans and known as a centaur to the Greeks. It has often been confused since classical times with Sagittarius.
Any of a group of icy bodies similar to both asteroids and comets, orbiting the Sun in elliptical paths mostly in the region between Saturn and Neptune. Centaurs range in diameter from around 100 to 400 km (62 to 248 mi) and are believed to be Kuiper belt objects that have escaped into the vicinity of the gas-giant planets. Centaurs are considered to have unstable orbits, and gravitational encounters with the large outer planets could send them into the inner solar system or alternatively could eject them from the solar system into interstellar space. Chiron, the first such body to be classified as a Centaur, was discovered in 1977.