Halley's comet[hălˈēz, hāˈlēz]
Halley's comet definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
a famous comet, last seen in 1986, whose reappearance about every 76 years was predicted by Edmond Halley
Halley's comet definition by American Heritage Dictionary
The American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
A comet with a period of approximately 76 years. The first comet for which a return was successfully predicted, it last appeared in 1986.
Origin: After Edmund Halley.
halley's comet - Science Definition
A short-period comet that orbits the Sun once every 76 years. It is visible to the unaided eye and last appeared in 1986, when close observation by spacecraft showed that its nucleus measures about 16 km (10 mi) by 8 km (5 mi) and is composed of water ice, stony minerals, and organic compounds. Its next appearance will be in the year 2061.