/ Dictionary / Index A addition compound: Meaning and Definition of Find definitions for: addi'tion com"pound Pronunciation: [key] — Chem. Chem. adduct (def. 2). Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. additional addition polymer Related Content Daily Word Quiz: secular Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language