Main Entry: Hy·dra

Pronunciation: \ˈhī-drə\

Function: noun

Etymology: Middle English Ydra, from Latin Hydra, from Greek

Date: 15th century

1 : 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
2 not capitalized : a multifarious evil not to be overcome by a single effort
3 [Latin (genitive Hydrae), from Greek] : a southern constellation of great length that lies south of Cancer, Sextans, Corvus, and Virgo and is represented on old maps by a serpent
4 not capitalized [New Latin, from Latin, Hydra] : any of numerous small tubular freshwater hydrozoan polyps (Hydra and related genera) having at one end a mouth surrounded by tentacles