[1] : WordNet (r) 2.0

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
see also:
sluicegate sluice valve penstock head gate water gate 

[2] : Moby Thesaurus II by Grady Ward, 1.0

46 moby thesaurus words for "floodgate":
   aboideau, air lock, avenue, blowhole, channel, chute, debouch,
   dock gate, door, egress, emunctory, escape, estuary, exhaust, exit,
   flood-hatch, flume, gate, head gate, lock, lock gate, loophole,
   opening, out, outcome, outfall, outgate, outgo, outlet, penstock,
   pore, port, sally port, sluice, sluice gate, spiracle, spout, tap,
   tide gate, vent, ventage, venthole, vomitory, water gate, way out,
   weir

Floodgate >> F Words
Floodgate, definition of term: Floodgate
floodgate_pag1.html