A sluice gate is commonly known as a floodgate, which is a barrier designed to control water flow. The term sluice gate can also be referred to as a penstock, which is a gate that regulates the flow of water or other fluids. Another synonym for sluice gate is a spillway, which is a structure designed to release excess water from a dam, reservoir or any other water retention structure. A flap gate is also a synonym for sluice gate, which is a vertical barrier hinged at the top, designed to restrict or allow the flow of water. In summary, sluice gate, floodgate, penstock, spillway, and flap gate all refer to a structure designed to control the flow of water.