poison gas
From Longman Dictionary of Contemporary EnglishRelated topics: Weaponspoison gasˌpoison ˈgas noun [uncountable] PMWgas that causes death or serious injury, used especially against an enemy in a war There are reports that poison gas is being used against the rebels.Examples from the Corpuspoison gas• A heavy overcast like a poison gas cloud was stationary over the battered city.• Whether it's against poison gas or pollution or radiation he can't say.• At the time, however, I feared poison gas.• It's a land where doom hangs upon the air like poison gas.• There was fear of poison gas, in a nation where Zyklon-B was part of the collective memory.