/ Dictionary / Index N NPK: Meaning and Definition of Find definitions for: NPK Pronunciation: [key] nitrogen, phosphorus, and potasium. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. NP n.p. or d. Related Content Daily Word Quiz: ounterfeit Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language