a gun, especially a shotgun with a short barrel, for quelling riots rather than inflicting serious injury.
Origin of riot gun
First recorded in 1925–30
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for riot gun
The Colonel ejected his words with the decisive click of a riot-gun.'Me-Smith'|Caroline Lockhart
Then he went in and got his riot-gun, well loaded with duck-shot.
So they raged all night, firing at the jail, but not daring to come too near the man with the riot-gun.