/ Dictionary / Index A addition reaction: Meaning and Definition of Find definitions for: addi'tion reac"tion Pronunciation: [key] — Chem. Chem. a reaction in which part of a compound is added to one end of a double or triple bond, while the rest adds to the other end, converting it, respectively, to a single or double bond. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. addition polymerization additive Related Content Daily Word Quiz: spectral Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language