Hydra

noun

1. (Greek mythology) monster with nine heads; when struck off each head was replaced by two new ones

   noun.person

   Examples

   Hydra was slain by Hercules.

   Source: WordNet 3.0

2. a long faint constellation in the southern hemisphere near the equator stretching between Virgo and Cancer

   noun.object

   Synonyms snake

   Source: WordNet 3.0

3. trouble that cannot be overcome by a single effort because of its many aspects or its persistent and pervasive quality

   noun.cognition

   Examples

   We may be facing a hydra that defies any easy solution.

   Source: WordNet 3.0

4. small tubular solitary freshwater hydrozoan polyp

   noun.animal

   Source: WordNet 3.0

5. A serpent or monster in the lake or marsh of Lerna, in the Peloponnesus, represented as having many heads, one of which, when cut off, was immediately succeeded by two others, unless the wound was cauterized. It was slain by Hercules. Hence, a terrible monster.

   noun

   Source: webster1913