/ Dictionary / Index D diagonal: Meaning and Definition of Find definitions for: di•ag•o•nal Pronunciation: (dī-ag'u-nl, -ag'nl), [key] — adj. connecting two nonadjacent angles or vertices of a polygon or polyhedron, as a straight line. extending from one edge of a solid figure to an opposite edge, as a plane. having an oblique direction. having oblique lines, ridges, markings, etc. —n. a diagonal line or plane. virgule. a diagonal row, part, pattern, etc. (of a horse at a trot) the foreleg and the hind leg, diagonally opposite, which move forward simultaneously. See a set of entries in a square matrix running either from upper left to lower rightor lower left to upper right one of the oblique lines of squares on a chessboard: He advanced his bishop along the open diagonal. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: diagonal (Thesaurus) diagnostics diagonal cloth Related Content Daily Word Quiz: impetuous Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language