柯林斯詞典nitrogen dioxide 1. N a red-brown poisonous irritating gas that, at ordinary temperatures, exists in equilibrium with dinitrogen tetroxide. It is an intermediate in the manufacture of nitric acid, a nitrating agent, and also an oxidizer for rocket fuels. Formula: NO2 二氧化氮 返回 nitrogen dioxide劍橋詞典a poisonous brown gas , formed when some metals dissolve in nitric acid 二氧化氮 返回 nitrogen dioxide