/ Dictionary / Index B back nine: Meaning and Definition of Find definitions for: back' nine' Pronunciation: [key] — Golf. Golf. the final nine holes on an eighteen-hole course. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. back mutation back number Related Content Daily Word Quiz: profiterole Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language