/ Dictionary / Index A additional: Meaning and Definition of Find definitions for: ad•di•tion•al Pronunciation: (u-dish'u-nl), [key] — adj. added; more; supplementary: additional information. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: additional (Thesaurus) addition addition compound 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