/ Dictionary / Index F flat-out: Meaning and Definition of Find definitions for: flat-out Pronunciation: (flat'out'), [key] — adj. Informal. moving or working at top speed or with maximum effort; all-out: a flat-out effort by all contestants. downright; thoroughgoing: Many of the paintings were flat-out forgeries. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: flat-out (Thesaurus) flatling flat-plate collector Related Content Daily Word Quiz: entomology Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language