(Greek mythology) monster with nine heads; when struck off each head was replaced by two new ones
Hydra was slain by Hercules.
source: WordNet 3.0
a long faint constellation in the southern hemisphere near the equator stretching between Virgo and Cancer
source: WordNet 3.0
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.
source: WordNet 3.0
small tubular solitary freshwater hydrozoan polyp
source: WordNet 3.0
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.
