What occurs when two opposing currents meet, causing water to rotate?

The phenomenon described in the question, where two opposing currents meet and cause water to rotate, is accurately characterized as whirlpools. When currents flow toward each other in a body of water, the interaction can create a localized area of turbulence where the water swirls in a circular motion. This swirling action is what commonly defines a whirlpool, and it can vary in intensity based on the strength and velocity of the opposing currents.

Eddies also involve rotation of water but are typically associated with the flow around obstacles in rivers or streams, leading to smaller swirling motions rather than the larger, more chaotic motion seen in whirlpools. Rapids, on the other hand, are characterized by an increase in velocity and turbulence of water over a decline, resulting in choppy water but not specifically in the rotational aspect described in the question. Aberrations generally refer to irregularities or deviations from the norm, which do not directly relate to the specific interaction of currents creating rotational motion. Thus, whirlpools are the most suitable answer to the question about the rotation of water due to two opposing currents.