/ Dictionary / Index L law of conservation of mass: Meaning and Definition of Find definitions for: law' of conserva'tion of mass' Pronunciation: [key] — Physics. Physics. See Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. law of conservation of linear momentum law of contradiction Related Content Daily Word Quiz: loathe Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language