- Hydra
(in ancient Greek stories 古希腊神话 a snake with several heads. As one head was cut off, another one grew. In the end it was killed by Hercules. 许德拉，多头蛇（砍去一个头即长出新头，后为大力神赫拉克勒斯所杀） - (formal)
a thing that is very difficult to deal with, because it continues for a long time or because it has many different aspects 棘手的复杂事物；难以根绝的祸患 - (
biology 生物 an extremely small water creature with a body that is like a tube in shape and tentacles around its mouth 水螅
Word Originvia Latin from Greek hudra ‘water snake’, named by Linnaeus because, if cut into pieces, each section can grow into a whole animal.