'Comet' definitions:

Definition of 'comet'

From: WordNet
noun
(astronomy) a relatively small extraterrestrial body consisting of a frozen mass that travels around the sun in a highly elliptical orbit

Definition of 'Comet'

From: GCIDE
  • 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. com[`e]te.] (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. [1913 Webster]