rain·for·est or rain forest (rān'fôr'ĭst, fŏr'-) n. A dense evergreen forest with an annual rainfall of at least 406 centimeters (160 inches). Rainforests are often, but not always, located in tropical regions.
1903, apparently a loan-translation of Ger. Regenwald, coined by A.F.W. Schimper for his 1898 work "Pflanzengeographie," and used first in the Eng. translation of it.