- floodgate - something that restrains a flood or outpouring; "suspension of surveillance opened the floodgates to illegal immigrants"
--1 is a kind of restraint
- sluicegate, sluice valve, floodgate, penstock, head gate, water gate - regulator consisting of a valve or gate that controls the rate of water flow through a sluice
--2 is a kind of regulator
--2 is a part of sluice, sluiceway, penstock - sluicegate, sluice valve, floodgate, penstock, head gate, water gate - regulator consisting of a valve or gate that controls the rate of water flow through a sluice