/ Dictionary / Index O OO gauge: Meaning and Definition of Find definitions for: OO gauge Pronunciation: (ō'ō'), [key] a model railroad gauge of in. (19 mm). Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. oogamete oogenesis 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