floodgate

Etymology

From Middle English flodegate, flodgate, flodeyate, floodȝate, flodȝete, equivalent to flood + gate.

noun

1. An adjustable gate or valve used to control the flow of water through a sluice.
   At the start of the Second World War floodgates would be installed at the ends of the under-Thames sections of the Bakerloo and Northern lines to save them from inundation should bombs damage the riverbed. 2012, Andrew Martin, Underground Overground: A passenger's history of the Tube, Profile Books, page 31
2. (by extension) Anything that controls or limits an outpouring of people, emotion etc.
   “The floodgates for advertising on cable are down,” says Michael Dann, a leading consultant on cable television. 1981-07-26, Sandra Salmans, “Will cable TV be invaded by commercials?”, in New York Times
3. (obsolete) A stream that passes through a floodgate; a torrent.
   The accuſation conſiſting of thoſe three articles, was moſt true: your doctrine was ſcādalous, it offred much offence, being generally diſtaſted; and was erroneous, being detected to be the floodgate of Traitors ſtaiers, looſing in ſome ſuppoſititious doctrines, and many blaſphemous arrogating much to man, derogating much from God. 1610, Daniell Price, The Defence of Truth Against a booke falsely called The Triumph of Truth sent over from Arras A.D. 1609 by Humfrey Leech late Minister. […], Oxford, Lib. 2 Cap. 3, page 237