hydra
noun
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.
hydra
American
[hahy-druh]
/ ˈhaɪ drə /
noun
-
hydras,
plural
-
hydrae,
plural
-
Hydrae
genitive
-
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.
Hydra
1
British
/ ˈhaɪdrə /
noun
hydra
2
British
/ ˈhaɪdrə /
noun
-
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
Hydra
3
British
/ ˈhaɪdrə /
noun
hydra
Scientific
/ hī′drə /
-
hydras
plural
Other Word Forms
Noun Inflected Forms
Etymology
Origin of hydra
First recorded in 1325–75; from Latin hydra, from Greek hýdrā “water serpent” (replacing Middle English ydre, from Middle French, from Latin); see otter
Vocabulary lists containing hydra
Elements of the Universe: Hydr, Hydro ("Water")
Looking to grow your vocabulary? Check out this interactive, curated word list from our team of English language specialists at Vocabulary.com – one of over 17,000 lists we've built to help learners worldwide!
Reading: Literature - Mythology - Introductory
Interested in learning more words like this one? Our team at Vocabulary.com has got you covered! You can review flashcards, quiz yourself, practice spelling, and more – and it's all completely free to use!
Reading: Literature - Mythology - Middle School
Want to remember this word for good? Start your learning journey today with our library of interactive, themed word lists built by the experts at Vocabulary.com – we'll help you make the most of your study time!
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
See Examples For:
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
Aside from giving housing and homelessness their own box atop Newsom’s organizational chart, the chief selling point of the reorganization has been to simplify the state’s hydra of affordable housing financing systems.
From Los Angeles Times ● Jul. 13, 2025
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
“We’ll consider this a dress rehearsal. Shall I unleash the hydra onto the Spanish Steps now?”
From "The Mark of Athena" by Rick Riordan
On an obscure research assignment, the narrator travels to the Greek island of Hydra to meet Theódoros Apostolakis, who has created a paradoxical museum for lost things.
From The Wall Street Journal ● Aug. 4, 2026
This white dwarf system lies about 200 light-years from Earth in the constellation Hydra.
From Science Daily ● Jan. 8, 2026
The Marvel universe more recently used the Nazi-like Hydra organization as a multiheaded big bad.
From New York Times ● Jun. 19, 2024
But it’s like cutting the heads off a Hydra.
From Seattle Times ● Aug. 20, 2023
Ella spotted Brigit surrounded by both the Hydra and Ursa Minor girls.
From "The Marvellers" by Dhonielle Clayton
Budding occurs commonly in some invertebrate animals such as corals and hydras.
From Textbooks ● Jun. 9, 2022
"Online services are like hydras, if you fix one problem, another one often emerges," James Mickens, a professor of computer science at Harvard, explains in a statement.
From BBC ● Sep. 9, 2021
Everyone in New York has heard about co-op boards that proved to be the most persnickety of the many many-headed hydras exerting authority over daily life.
From New York Times ● May 8, 2016
The name van Leeuwenhoek gave them was “polyps,” though they would eventually be commonly known as hydras.
From Salon ● Jan. 17, 2016
The walls were lined with metal shelves six stories high, decorated with war banners, painted shields, and the stuffed heads of dragons, hydras, giant lions, and wild boars.
From "The Son of Neptune" by Rick Riordan
The infalling matter collides with other material bound to the white dwarf, forming tall columns of hot gas that emit intense X-rays, making systems like EX Hydrae ideal targets for IXPE.
From Science Daily ● Jan. 8, 2026
EX Hydrae exists in a binary system alongside a normal main sequence star.
From Science Daily ● Jan. 8, 2026
In EX Hydrae, the magnetic field is not strong enough to direct all incoming material onto the star's magnetic poles.
From Science Daily ● Jan. 8, 2026
The mission's ability to measure the polarization of X-rays allowed astronomers to closely examine EX Hydrae, a type of system known as an intermediate polar.
From Science Daily ● Jan. 8, 2026
You saw that big Beta Hydrae orrery at Kankad's observatory.
From Uller Uprising by John D. Clark
Random Word
Spin the wheel and learn a new word!
Get a wordDefinitions 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.
