Nerve gas is a poisonous gas used in war as a weapon.
nerve gas in British English
noun
(esp in chemical warfare) any of various poisonous gases that have a potentially fatal paralysing effect on the central nervous system
nerve gas in American English
any of several poisonous, odorless, colorless, and tasteless liquids that volatilize readily, are rapidly absorbed through the eyes, lungs, or skin, and inactivate the enzyme cholinesterase, causing paralysis of the respiratory and central nervous systems: manufactured as for use in war as a chemical weapon