/ Dictionary / Index O O horizon: Meaning and Definition of Find definitions for: O horizon Pronunciation: [key] the layer of loose leaves and organic debris at the surface of soil. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. ohone Ohře Related Content Daily Word Quiz: perspicacious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language