/ Dictionary / Index C cloud nine: Meaning and Definition of Find definitions for: cloud' nine' Pronunciation: [key] — Informal. Informal. a state of perfect happiness (usually in the phrase on cloud nine). Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. cloudlet cloud physics Related Content Daily Word Quiz: labyrinth Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language