/ Dictionary / Index N NIA: Meaning and Definition of Find definitions for: NIA Pronunciation: [key] National Intelligence Authority. Newspaper Institute of America. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Ni niacin Related Content Daily Word Quiz: soporific Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language