Classical Mythology. Often Hydra a water or marsh serpent with nine heads, each of which, if cut off, grew back as two; Hercules killed this serpent by cauterizing the necks as he cut off the heads.
any freshwater polyp of the genus Hydra and related genera, having a cylindrical body with a ring of tentacles surrounding the mouth, and usually living attached to rocks, plants, etc., but also capable of detaching and floating in the water.
a persistent or many-sided problem that presents new obstacles as soon as one aspect is solved.
(initial capital letter) the Sea Serpent, a large southern constellation extending through 90° of the sky, being the longest of all constellations.
any solitary freshwater hydroid coelenterate of the genus Hydra, in which the body is a slender polyp with tentacles around the mouth
a persistent trouble or evil
the hydra of the Irish problem
First recorded in 1325–75; from Latin hydra, from Greek hýdrā “water serpent” (replacing Middle English ydre, from Middle French, from Latin); see otter
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Samar shares the popular view that for every senior official "they've reportedly assigned three to seven successors. Like a hydra - you cut one head off, another grows back. They won't surrender any time soon."
From BBC • Mar. 25, 2026
"In 20 years, and despite the resolute efforts of our police officers, gendarmes, judges, teachers and elected officials, the antisemitic hydra has kept advancing," he said.
From Barron's • Feb. 13, 2026
“Like the hydra, when you cut one head off and two more grow in its place. That’s what all of us are working towards.”
From Los Angeles Times • Jul. 24, 2023
This suggests that evolution plays around with these chemical pathways, altering them over the hundreds of millions of years since the hydra and human lineages diverged from each other on the evolutionary tree.
From Scientific American • Jun. 16, 2023
She also kept a fight from breaking out between the children of Mars and the children of Ares over the best way to kill a hydra.
From "Blood of Olympus" by Rick Riordan
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
