Any of several perennial water plants of the genus Trapa (family Trapaceae), native to Europe, Asia, and Africa, or their edible, nutlike fruit.
The water caltrop ( T. natans ) has two sets of leaves
long, feathery, rootlike, submerged leaves and a loose rosette of floating leaves attached to leafstalks 2–4 in (5–10 cm) long. The small fruit usually has four spiny angles. The Chinese water chestnut ( Eleocharis tuberosus or E. dulcis ) is a member of the sedge family .