Water chestnut \Wa"ter chest"nut\ (Bot.) 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}.
Trapa bicornis n : water chestnut whose spiny fruit has two rather than 4 prongs [syn: {ling}, {ling ko}]