Each of the seven oxides of nitrogen; specifically any one or a mixture of these oxides released into the environment as a result of fuel combustion (especially nitric oxide, NO, and nitrogen dioxide, NO₂).
Origin
Mid 19th century.
Definition of nitrogen oxide in US English:
nitrogen oxide
noun
Each of the seven oxides of nitrogen; specifically any one or a mixture of these oxides released into the environment as a result of fuel combustion (especially nitric oxide, NO, and nitrogen dioxide, NO₂).