noun

• (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.
  "And They made by the lifting of Their hands, each god according to his sign, the Bright One with the flaring tail to seek from the end of the Worlds to the end of them again, to return again after a hundred years. Man, when thou seest the comet, know that another seeketh besides thee nor ever findeth out."

name

• (programming) A web application model in which a long-held HTTP request allows a web server to push data to a browser, without the browser explicitly requesting it.