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

"Hydra was slain by Hercules"

Category: People

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

Related Noun(s):snake

Category: Objects

3.Definition: small tubular solitary freshwater hydrozoan polyp

Category: Animals

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

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

Category: General