Comet

Com″et (?), n. [L. cometes, cometa, from Gr. � comet, prop. long-haired, fr. � to wear long hair, fr. � hair, akin to L. coma: cf. F. comète.] (Astron.) A member of the solar system which usually moves in an elongated orbit, approaching very near to the sun in its perihelion, and receding to a very great distance from it at its aphelion. A comet commonly consists of three parts: the nucleus, the envelope, or coma, and the tail; but one or more of these parts is frequently wanting. See Illustration in Appendix.