/ Dictionary / Index F flat back: Meaning and Definition of Find definitions for: flat' back" Pronunciation: [key] a book spine presenting a completely flat surface. a book bound with such a spine. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. flat arch flatbed Related Content Daily Word Quiz: agitated Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language