Coriolis effect
The change in rotor blade velocity to compensate for a change in the distance between the center of mass of the rotor blade and the axis rotation of the blade as the blades flap in flight.
Aviation Maintenance Technician Handbook — Airframe, p. G-10
Also defined in 1 more source
The tendency of a rotor blade to increase or decrease its velocity in its plane of rotation when the center of mass moves closer to or farther from the axis of rotation.