/ Dictionary / Index N nitrogen fixer: Meaning and Definition of Find definitions for: ni'trogen fix"er Pronunciation: [key] any of various microorganisms in the soil involved in the process of nitrogen fixation. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. nitrogen fixation nitrogen-fixing Related Content Daily Word Quiz: eureka Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language