water cannon definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
a pumping device which produces a powerful jet of water, used as by the police to disperse crowds
water cannon definition by American Heritage Dictionary
A truck-mounted apparatus that fires water at high pressure, used especially to disperse crowds or control rioters.