water chestnut noun Date: 1854 any of a genus ( Trapa, especially T. natans of the family Trapaceae, the water-chestnut family) of Old World aquatic herbs sometimes grown as ornamentals, a whitish crunchy vegetable used especially in Chinese cooking that is the peeled and often sliced tuber of a sedge ( Eleocharis dulcis syn. E. tuberosa ) native to Asia but widely cultivated elsewhere
