柯林斯词典sea urchin (sea urchins) 1. N-COUNT A sea urchin is a small round sea creature that has a hard shell covered with sharp points. 海胆 返回 sea urchin剑桥词典a small sea creature that lives in water that is not very deep , has a round shell covered with sharp points like needles , and has flesh that can be eaten 海胆 返回 sea urchin