Nitrogen Oxide

The term nitrogen oxide is used to refer to any of these oxygen compounds of nitrogen, or to a mixture of them:Nitric oxide (NO), nitrogen(II) oxideNitrogen dioxide (NO2), nitrogen(IV) oxideNitrous oxide (N2O)Dinitrogen trioxide (N2O3), nitrogen(II, IV) oxideDinitrogen tetroxide (N2O4), nitrogen(IV) oxideDinitrogen pentoxide (N2O5), nitrogen(V) oxide (Note that the last three are unstable.)
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Noun
1. any of several oxides of nitrogen formed by the action of nitric acid on oxidizable materials; present in car exhausts
(hypernym) oxide

The result of photochemical reactions of nitric oxide in ambient air; major component of photochemical smog. Product of combustion from transportation and stationary sources and a major contributor to the formation of ozone in the troposphere and to acid deposition.