- any aquatic plant of the genus Trapa, bearing an edible, nutlike fruit, especially T. natans, of the Old World.
- the fruit itself.
- a floating aquatic onagraceous plant, Trapa natans, of Asia, having four-pronged edible nutlike fruits
- a Chinese cyperaceous plant, Eleocharis tuberosa, with an edible succulent corm
- the corm of the Chinese water chestnut, used in Oriental cookery
