Meaning of nitrogen dioxide

ni'trogen diox'ide

Pronunciation: [key]
— Chem. Chem.
  1. a reddish-brown, highly poisonous gas, NO, used as an intermediate in the manufacture of nitric and sulfuric acids, and as a nitrating and oxidizing agent; a major air pollutant from the exhaust of internal combustion engines that are not fitted with pollution control devices.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.