Definition of: comet

(kom′it) noun Astron.
A celestial body drawn within the sun's gravitational field and occasionally close enough to the earth or bright enough to be observed by the naked eye. It consists of a nucleus of more or less condensed material, accompanied by a tenuous coma which always points in a direction away from the sun. A number of periodic comets are now known: among them are Biela's comet, with a period of 7 years; Encke's comet, period 3 years; Halley's comet, period 76 years. [OE cometa <L <Gk. komētēs long–haired <komē hair]
—com·et·ar·y (kom′ə·ter′ē), co·met·ic (kə·met′ik) adjective