Source : WordNet®

floodgate
     n 1: something that restrains a flood or outpouring; "suspension
          of surveillance opened the floodgates to illegal
          immigrants"
     2: regulator consisting of a valve or gate that controls the
        rate of water flow through a sluice [syn: {sluicegate}, {sluice
        valve}, {penstock}, {head gate}, {water gate}]