around means going in a circle and one way to memorize the definition for around is if you take off the a it spells round and round as in a circle and the definition is to go around in a circle.

I assume that you are asking about the definition of a circle. A circle is a locus of points in a plane that are at a constant distance from a fixed point.

The precise definition of the word 'centres' is the middle point of a circle or a sphere. This means the point is an equal distance from every point on the circle/sphere.