nitrogen fixation

WordReference Random House Unabridged Dictionary of American English © 2025

ni′trogen fixa′tion, 

1. any process of combining atmospheric nitrogen with other elements, either by chemical means or by bacterial action: used chiefly in the preparation of fertilizers, industrial products, etc.
2. this process as performed by certain bacteria found in the nodules of leguminous plants, which make the resulting nitrogenous compounds available to their host plants.
• 1890–95

Collins Concise English Dictionary © HarperCollins Publishers::

nitrogen fixation noun

1. the conversion of atmospheric nitrogen into nitrogen compounds by certain bacteria, such as Rhizobium in the root nodules of legumes
2. a process, such as the Haber process, in which atmospheric nitrogen is converted into a nitrogen compound, used esp for the manufacture of fertilizer