/ Dictionary / Index D Diels-Alder reaction: Meaning and Definition of Find definitions for: Diels'-Al'der reac"tion Pronunciation: (dēlz'äl'dur), [key] — Chem. Chem. the reaction in which a conjugated diene combines with a double or triple bond of a given compound to form a ring of six carbon atoms. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Diels Dien Bien Phu Related Content Daily Word Quiz: philtrum Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language