HYDRA

I. noun Etymology: Middle English Ydra, from Latin ~, from Greek Date: 15th century a many-headed serpent or monster in Greek mythology that was slain by Hercules and each head of which when cut off was replaced by two others, a multifarious evil not to be overcome by a single effort, a southern constellation of great length that lies south of Cancer, Sextans, Corvus, and Virgo and is represented on old maps by a serpent, any of numerous small tubular freshwater hydrozoan polyps ( ~ and related genera) having at one end a mouth surrounded by tentacles, II. geographical name or Modern Greek Ídhra island Greece in S Aegean Sea off E coast of Peloponnese area 20 square miles (52 square kilometers ), population 2794 , Hydriot or Hydriote noun