from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. Greek Mythology The many-headed monster that was slain by Hercules.
  • n. A constellation in the equatorial region of the southern sky near Cancer, Libra, and Centaurus. Also called Snake2.
  • n. A persistent or multifaceted problem that cannot be eradicated by a single effort.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • proper n. A taxonomic genus within the family Hydridae — predatory freshwater cnidarians, thought not to age, the hydras.
  • proper n. A mythological serpent with seven heads, slain by Hercules as one of his twelve labours. Also called the Lernaean Hydra.
  • proper n. A spring constellation of the northern sky, said to resemble a serpent. It lies just south of the zodiac and contains the star Alphard.
  • proper n. The name of one of Pluto's moons. (Named 21 June 2006).


Middle English Idra, from Latin Hydra, from Greek Hudrā, Hydra, a water serpent.
(American Heritage® Dictionary of the English Language, Fourth Edition)
From Latin Hydra, the mythical serpent. (Wiktionary)
From Latin Hydra, the mythical serpent, originally from Ancient Greek Ὕδρα. (Wiktionary)


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