/ Dictionary / Index T triangular matrix: Meaning and Definition of Find definitions for: trian'gular ma'trix Pronunciation: [key] — Math. Math. a square matrix in which either all the entries above the principal diagonal, or all the entries below the principal diagonal, are zero. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. triangular triangular trade Related Content Daily Word Quiz: blithesome Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language