waterfall, area where flowing river water drops abruptly and nearly vertically (see video).ver flow.

A waterfall is a river or other body of water's steep fall over a rocky ledge into a plunge pool below. Waterfalls are also called cascades. The process of erosion, the wearing away of earth, plays an important part in the formation of waterfalls. ... Often, waterfalls form as streams flow from soft rock to hard rock.