/ Dictionary / Index S second law of motion: Meaning and Definition of Find definitions for: sec'ond law' of mo'tion Pronunciation: [key] — Physics. Physics. See under Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. second language second law of thermodynamics Related Content Daily Word Quiz: arboreal Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language