Sheer Descent©
This is technically the brand name of a smooth, linear-flowing waterfall manufactured by the Jandy/Zodiac Corporation. However, much like the term Kleenex, a sheer descent now often simply refers to any straight, linear waterfall, regardless of the manufacturer.
Most popular as a simple arching waterfall that comes out of a raised sidewall of the swimming pool, a sheer descent might also be mounted overhead, to produce a water wall effect. (See also Rain Wall.)