An eddy is a circular current of water or air that moves against the main flow, creating a small whirlpool or swirl. Picture a river flowing past a large rock: behind that rock, the water curves back on itself, spinning in circles while the rest of the river rushes straight ahead. That swirling pocket is an eddy.

Kayakers and canoeists learn to use eddies as resting spots in fast-moving rivers. By paddling into an eddy behind a boulder, they can escape the main current and catch their breath before continuing downstream. The calm water inside an eddy can feel almost magical, spinning gently while the powerful current roars just a few feet away.

Air creates eddies too. Wind swirling around a tall building forms eddies that can scatter leaves in spiraling patterns. When you watch smoke rise from a candle and suddenly curl back on itself, you're seeing an eddy form.

Sometimes people use eddy as a verb, saying that water or air eddies around an obstacle.