1. the chemical process in which a nitro group is added to an organic compound (or substituted for another group in an organic compound) • Derivationally related forms: nitrify • Hypernyms: chemical process, chemical change, chemical action 2. the oxidation of ammonium compounds in dead organic material into nitrates and nitrites by soil bacteria (making nitrogen available to plants) • Derivationally related forms: nitrify • Topics: plant, flora, plant life • Hypernyms: oxidation, oxidization, oxidisation