What term describes a current that moves in a circular motion or against the main current?

The term that describes a current that moves in a circular motion or against the main current is "eddy." An eddy is a small, swirling current of water that occurs when the flow of the main current is disrupted, often by an obstacle like a rock or the riverbank. Eddies can be found in various water bodies, including rivers and oceans, and they can be important in understanding how water interacts with its environment and other currents.

In contrast, "current" generally refers to the flow of water in a specific direction, without the circular motion characteristic of an eddy. "Stream" refers to a body of water flowing in a channel, which doesn't inherently describe the swirling motion. "Tide" describes the periodic rise and fall of sea levels caused by gravitational forces but does not refer to circular motion or flowing against the main current. Therefore, "eddy" is distinctly the correct term for this specific behavior of water currents.