Instantaneous Center of Rotation
Every point on a rotating rigid body has the same angular velocity, w, which can be a function of time.
In fact, for any rigid body in plane motion there is a common reference point about which all points on this body are rotating.
This point is the instantaneous center of rotation or the instantaneous center of zero velocity.
The instantaneous center can be found as long as you know the velocity vector at 2 different points or if you know the velocity of 1 point and the angular velocity of the body.