hydra

n 1 (in Greek mythology) snake-like monster with many heads that grew again if they were cut off （希腊神话中的）蛇怪（长著许多头, 斩去後能重新长出）. 2 (fig 比喻) thing that is hard to get rid of; recurring problem 难以除掉的事物; 一再出现的问题.

hush-money, husk, huskily, huskiness, husky, hussar, hussy, hustings, hustle, hustler, hut, hutch, hutment, hutted, hyacinth, hyaena, hybrid, hybridize, hybridise, Hyde Park, hydr(o)-, hydrangea, hydrant, hydrate, hydration, hydraulic, hydraulically, hydraulics, hydrocarbon, hydrochloric, hydroelectric, hydroelectrically, hydroelectricity, hydrofoil, hydrogen, hydrogen bomb (also H-bomb), hydrogen peroxide, hydrometer, hydrophobia, hydroplane, hydroponics,