From Longman Dictionary of Contemporary Englishwater cannonˈwater ˌcannon noun [countable, uncountable] PMWSCPa machine that sends out a powerful stream of water, used by police to control violent crowds
Examples from the Corpus
water cannon• The Army moved in with a water cannon and tear gas, forcing the marchers into hasty retreat.• The bomb squad took the device to the basement and disarmed it by inundating it with a water cannon.• There, they were surrounded by sand bags and soaked with a water cannon, which disabled the devices.• Police units used teargas and water cannon against the crowds and over 200 people were arrested.• Detachments of police went after individuals and when the street was nearly clear, water cannon were brought in.• As demonstrations escalated, water cannon and fire engines appeared.• There were no plastic riot shields, no riot sticks or helmets, no water cannon and no mobile command posts available.• Children and adults were beaten by police and knocked from their feet by powerful water cannon manipulated by their fireman accomplices. 