/ Dictionary / Index B back number: Meaning and Definition of Find definitions for: back' num'ber Pronunciation: [key] an out-of-date issue of a serial publication. anything out-of-date. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. back nine back o' beyond Related Content Daily Word Quiz: rustic Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language