/ Dictionary / Index A addnl.: Meaning and Definition of Find definitions for: addnl. Pronunciation: [key] additional. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. addn. add-on Related Content Daily Word Quiz: fervor Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language