Hydra

(noun) (Greek mythology) monster with nine heads; when struck off each head was replaced by two new ones. Example: "Hydra was slain by hercules."

(noun) a long faint constellation in the southern hemisphere near the equator stretching between Virgo and Cancer. Synonyms: Snake.

(noun) trouble that cannot be overcome by a single effort because of its many aspects or its persistent and pervasive quality. Synonyms: hydra. Example: "We may be facing a hydra that defies any easy solution."

(noun) small tubular solitary freshwater hydrozoan polyp. Synonyms: hydra.