/ Dictionary / Index O Oort cloud: Meaning and Definition of Find definitions for: Oort' cloud" Pronunciation: (ôrt, ōrt), [key] — Astron. Astron. a region of the solar system far beyond the orbit of Pluto in which billions of comets move in nearly circular orbits unless one is pulled into a highly eccentric elliptical orbit by a passing star. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. oops oory Related Content Daily Word Quiz: fervor Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language