Hydra Common

(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

"As an amateur astronomer, I spent last night scanning the southern sky to locate the elusive Hydra constellation nestled between Virgo and Cancer."

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

"The biologist carefully extracted a hydra from the pond water to examine its delicate tentacles under the microscope."

Any of several small freshwater polyps of the genus Hydra and related genera, having a naked cylindrical body and an oral opening surrounded by tentacles.

"The curious child watched in awe as the tiny hydra extended its delicate tentacles to catch a passing water flea."