An eddy is most commonly a swirling, circular movement in water or air that runs against or around the main flow, like a small whirlpool in a river or when water circles near a rock.

Basic meaning

  • In physics and fluid dynamics, an eddy is a rotating flow that forms when a moving fluid passes an obstacle and curls back on itself.
  • Everyday examples include whirlpools behind rocks in rivers, swirling water near a bridge pier, or circular motions in clouds and smoke.

Simple real‑life examples

  • The little whirlpool you see near the drain when bath water runs out is an eddy.
  • When a fast river flows past a big rock, calmer circular pools that form just behind the rock are eddies, often used by fish to rest and feed.
  • In the ocean, eddies are large circular currents that can bring deep, nutrient‑rich water up toward the surface.

Other uses of “Eddy”

  • Dictionaries also use eddy metaphorically for any circular or contrary “current” of activity or even thought, not just in water or air.
  • The word is pronounced the same as the name “Eddie,” so in some contexts it can be a person’s name, but as a thing , it mainly refers to that swirling current.

TL;DR: An eddy is a swirling, often circular, current in water or air that moves differently from the main flow, like a small whirlpool behind an obstacle.