# nitrogen dioxide

> English word · Noun

## Definitions
1. The binary compound NO₂, a brownish gas that is a poisonous air pollutant; it exists in equilibrium with dinitrogen tetroxide. It can be the poisonous result of a nitric acid spill contacting ambient air.

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/nitrogen-dioxide