- (n.) Any small fresh-water hydroid of the genus Hydra, usually found attached to sticks, stones, etc., by a basal sucker.
- (n.) 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.
- (n.) Hence: A multifarious evil or an evil having many sources; not to be overcome by a single effort.
- (n.) A southern constellation of great length lying southerly from Cancer, Leo, and Virgo.
Webster's Revised Unabridged Dictionary
| APA | Webster's. (2011). hydra. Retrieved September 21, 2026, from http://smartdefine.org/hydra/definitions/2017969 |
| Chicago | Webster's. 2011. "hydra" http://smartdefine.org/hydra/definitions/2017969 (accessed September 21, 2026). |
| Harvard | Webster's 2011, hydra, Smart Define, viewed 21 September, 2026, <http://smartdefine.org/hydra/definitions/2017969>. |
| MLA | Webster's. "hydra" 27 May 2011. Web. 21 September 2026. <http://smartdefine.org/hydra/definitions/2017969> |