a moving mass of icy cosmic debris thought to exist in the vast region beyond Pluto and to be the source of the comets that orbit the sun
Webster’s New World College Dictionary, Fourth Edition, compiled by the
editors of Webster’s New World Dictionaries. Copyright © 2010 by Houghton
Mifflin Harcourt. Published by Houghton Mifflin Harcourt. All rights reserved.
Word origin of 'Oort cloud'after J. Oort (1900-92), Du astronomer