Electricity The rotating part of a dynamo, consisting essentially of copper wire wound around an iron core. Electricity The moving part of an electromagnetic device such as a relay, buzzer, or loudspeaker. Electricity A piece of soft iron connecting the poles of a magnet. Biology A protective covering, structure, or organ of an animal or a plant, such as teeth, claws, thorns, or the shell of a turtle. A framework serving as a supporting core for the material that is used to make a sculpture.