A 'roundabout' is:

A roundabout is a circular intersection where vehicles travel counter-clockwise around a central island and yield to traffic already in the circle. Roundabouts replace traditional intersections and traffic signals in many places because they have fewer conflict points than four-way intersections, slow traffic to a safer speed (typically 15–25 mph), reduce serious crashes (fewer head-on or T-bone collisions), and keep traffic flowing without waiting for signals. Approach a roundabout in the correct lane (right lane for right turns and continuing, left lane for left turns or U-turns), yield to traffic already in the circle, enter when there is a safe gap, and exit by signaling and moving to the right lane. Pedestrians cross at the entries, not within the circle.