water chestnut

1. ☆
   1. a Chinese sedge (Eleocharis dulcis) with erect, cylindrical leaves, growing in dense clumps in water
   2. the large, button-shaped, submerged tubers of this plant, used in Chinese cooking
2. a floating aquatic weed (Trapa natans) of the water-chestnut family, with black, hard, horned fruit, the seed of which is sometimes eaten

adjective