Water chestnut

The fruit of Trapa natans and Trapa bicornis, Old World water plants bearing edible nutlike fruits armed with several hard and sharp points; also, the plant itself; -- called also water caltrop.

edible bulbous tuber of a Chinese marsh plant

a plant of the genus Trapa bearing spiny four-pronged edible nutlike fruits

Chinese sedge yielding edible bulb-shaped tubers