/ Dictionary / Index F flood plain: Meaning and Definition of Find definitions for: flood' plain" Pronunciation: [key] a nearly flat plain along the course of a stream or river that is naturally subject to flooding. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: floodplain (Thesaurus) floodlight projector flood tide Related Content Daily Word Quiz: tenacious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language