ni ‧ tro ‧ gen /ˈnaɪtrədʒ ə n/ BrE AmE noun [uncountable]
[ Date: 1700-1800 ; Language: French ; Origin: nitrogène , from nitre ( NITIC ACID ) + -gène 'producing' ]
a gas that has no colour or smell, and that forms most of the Earth’s air. It is a chemical ↑ element : symbol N