/ Dictionary / Index D diag.: Meaning and Definition of Find definitions for: diag. Pronunciation: [key] diagonal; diagonally. diagram. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. diaeresis diagenesis Related Content Daily Word Quiz: agitated Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language