/ Dictionary / Index L law of diminishing marginal utility: Meaning and Definition of Find definitions for: law' of dimin'ishing mar'ginal util'ity Pronunciation: [key] — Econ. Econ. the law that for a single consumer the marginal utility of a commodity diminishes for each additional unit of the commodity consumed. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. law of definite composition law of diminishing returns Related Content Daily Word Quiz: labyrinth Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language