[hahy-druh] 
[-dree] for 1–3, genitive -drae [-dree] for 4. | 1. | (often initial capital letter ) Classical Mythology. a water or marsh serpent with nine heads, each of which, if cut off, grew back as two; Hercules killed this serpent by cauterizing the necks as he cut off the heads. |
| 2. | any freshwater polyp of the genus Hydra and related genera, having a cylindrical body with a ring of tentacles surrounding the mouth, and usually living attached to rocks, plants, etc., but also capable of detaching and floating in the water. |
| 3. | a persistent or many-sided problem that presents new obstacles as soon as one aspect is solved. |
| 4. | (initial capital letter) Astronomy. the Sea Serpent, a large southern constellation extending through 90° of the sky, being the longest of all constellations. |
| hy·dra (hī'drə) n. pl. hy·dras or hy·drae (-drē) Any of several small freshwater polyps of the genus Hydra and related genera, having a naked cylindrical body and an oral opening surrounded by tentacles. [New Latin Hydra, genus name, from Latin Hydra, Hydra; see Hydra.] |
| hydra (hī'drə) Pronunciation Key
Plural hydras or hydrae (hī'drē) See under hydroid. |