barrage balloon[bə räz̸h′, -räj′]
barrage balloon 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.
any of a number of anchored balloons with cables or nets attached for entangling low-flying attacking airplanes
barrage balloon definition by American Heritage Dictionary
A balloon anchored singly or in a series over a military objective to support nets that hinder the passage of enemy aircraft.