BAYOU (bi'oo), a marshy offshoot of a river. The term is used chiefly in the southern United States for an "ox-bow" lake left behind by a river that has abandoned its old channel in the lower stages of its course. Good examples are found in the lower Mississippi valley. In the lower reaches of a river where the country is more or less level, and the current slow, a river usually swings from side to side of its valley line in a series of curves, and in flood times there is a tendency for the water to impinge more strongly upon the concave bank. This bank will be eaten away, and the process will be repeated until finally it is cut through, leaving a loop or ox-bow lake filled with dead water, while the stream runs directly past it.