a : a piece of soft iron or steel that connects the poles of a magnet or of adjacent magnets
b : a usually rotating part of an electric machine (such as a generator or motor) which consists essentially of coils of wire around a metal core and in which electric current is induced or in which the input current interacts with a magnetic field to produce torque
c : the movable part of an electromagnetic device (such as a loudspeaker)
d : a framework used by a sculptor to support a figure being modeled in a plastic material