Synonyms for Water Chestnut (same or very similar meaning)
WordNet sense 1 (a plant of the genus Trapa bearing spiny four-pronged edible nutlike fruits):
caltrop, water chestnut plantWordNet sense 2 (Chinese sedge yielding edible bulb-shaped tubers):
Chinese water chestnut, Eleocharis dulcisFrom the ODE community, based on WordNetadd/edit