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

[ Syn: hydra ]

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

[ Syn: hydra , 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