Water chestnut:

bí qí

Also known as "horseshoe" and "ground chestnut". Monocotyledonous plant, Cyperaceae. Perennial aquatic herb. Grows in swamps or shallow water with clusters of stems. There are stolons underground, and the tops expand into oblate tubers. Tubers are rich in starch and can be eaten raw or cooked, and the starch can also be extracted or used for medicinal purposes.

Haha, I looked it up in the dictionary!~~~~~~~~~~~~~~~~~~^_^