/ Dictionary / Index L law of excluded middle: Meaning and Definition of Find definitions for: law' of exclud'ed mid'dle Pronunciation: [key] — Logic. Logic. the principle that any proposition must be either true or false. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. law of diminishing returns law of exponents Related Content Daily Word Quiz: languid Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language