What is Rotation?

Legal Definition
A rotation is a circular movement of an object around a center (or point) of rotation . A three-dimensional object always rotates around an imaginary line called a rotation axis. If the axis passes through the body's center of mass, the body is said to rotate upon itself, or spin. A rotation about an external point, e.g. the Earth about the Sun, is called a revolution or orbital revolution, typically when it is produced by gravity. The axis is called a pole.
-- Wikipedia
Legal Definition
The completion of one cycle, route, process or circuit.