/ Dictionary / Index N NIH: Meaning and Definition of Find definitions for: NIH Pronunciation: [key] National Institutes of Health. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: nih (Thesaurus) nigrosine nihilism Related Content Daily Word Quiz: vertigo Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language