An oxbow lake is a U-shaped body of water formed when a wide meander from the mainstem of a river is cut off to create a lake. This landform is called an oxbow lake for the distinctive curved shape that results from this process. In Australia, an oxbow lake is called a billabong. By itself, the word oxbow can also mean a U-shaped bend in a river or stream, whether or not it is cut off from the main stream