/ Dictionary / Index N NIOSH: Meaning and Definition of Find definitions for: NIOSH Pronunciation: (nī'osh), [key] — n. National Institute for Occupational Safety and Health. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Nios nip Related Content Daily Word Quiz: paradox Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language