1. (n.) The many-headed monster slain by Hercules; also a genus of small freshwater polyps\; a serpent or monster in the lake or marsh of Lerna, in the Peloponnesus, represented as having many heads, one of which, when cut off, was immediately succeeded by two others, unless the wound was cauterized. It was slain by Hercules. Hence, a terrible monster.

2. (n.) Hence: A multifarious evil, or an evil having many sources; not to be overcome by a single effort.

3. (n.) Any small fresh-water hydroid of the genus Hydra, usually found attached to sticks, stones, etc., by a basal sucker.

4. (n.) A southern constellation of great length lying southerly from Cancer, Leo, and Virgo.

Antlia Antlia Pneumatica Apus Aquarius Ara Caela Sculptoris Caelum Camelopardus Cancer Columba Noae Corona Australis Corona Borealis Corvus Crater Crux Dorado Draco Equuleus Gemini Grus Hercules Horologium Hydra Lacerta Leo Leo Minor Lepus Libra Little Dipper Lupus Lynx Lyra Malus Mensa Microscopium Monoceros Musca Norma Northern Cross Octans Ophiuchus Orion Pegasus Phoenix Reticulum Sagittarius Scorpius Sculptor Scutum Sextans Southern Cross Taurus Telescopium Triangulum Triangulum Australe Tucana Ursa Major Ursa Minor Vela Virgo Volans Vulpecula the Balance the Bull the Crane the Cross the Crow the Cup the Dragon the Fly the Foal the Hare the Indian the Lion the Lizard the Lynx the Lyre the Mast the Octant the Rule the Sails the Sea Serpent the Serpent the Serpent Bearer the Sextant the Southern Crown the Swan the Table the Telescope the Toucan the Twins the Unicorn the Virgin the Water Bearer the Wolf the Wreath