Variant of Hydra
- Gr. Myth. the nine-headed serpent slain by Hercules as one of his twelve labors: when any one of its heads is cut off, it is replaced by two others
- a long S constellation between Cancer and Libra: the largest constellation
- any persistent or ever-increasing evil with many sources and causes
- any of a family (Hydridae) of small, freshwater, solitary hydroids having a dominant soft-bodied polyp stage
Origin: Middle English ydre (from Old French from L), ydra from Classical Latin Hydra from Gr, water serpent, akin to hydōr, water
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