comet

Etymology

From Middle English comete, partly from Old English comēta and partly from Old French comete, both from Latin comētēs, from Ancient Greek κομήτης (komḗtēs, “longhaired”), short for ἀστὴρ κομήτης ([astēr] komētēs, "longhaired [star])" and referring to the tail of a comet, from κόμη (kómē, “hair”). Compare English faxed star.

noun

1. (astronomy) A small Solar System body consisting mainly of volatile ice, dust and particles of rock whose very eccentric solar orbit periodically brings it close enough to the Sun that the ice vaporises to form an atmosphere, or coma, which may be blown by the solar wind to produce a visible tail.
2. A celestial phenomenon with the appearance of such a body.
3. Any of several species of hummingbird found in the Andes.