/ Dictionary / Index L law of sines: Meaning and Definition of Find definitions for: law' of sines' Pronunciation: [key] — Trigonom. Trigonom. a law stating that the ratio of a side of a plane triangle to the sine of the opposite angle is the same for all three sides. a law stating that the ratio of the sine of an arc of a spherical triangle to the sine of the opposite angle is the same for all three arcs. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. law of segregation law of superposition Related Content Daily Word Quiz: acerbity Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language