Definition of Hydra (noun)
- (Greek mythology) monster with nine heads; when struck off each head was replaced by two new ones
- "Hydra was slain by Hercules"
- a long faint constellation in the southern hemisphere near the equator stretching between Virgo and Cancer
- synonyms: Snake
- 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"
- small tubular solitary freshwater hydrozoan polyp
Source: Princeton University Wordnet