Insulator

From insulate 'to isolate' (itself from Latin insula 'island') + suffix -or

Full definition of insulator

(plural insulators)

A substance that does not transmit heat (thermal insulator), sound (acoustic insulator) or electricity (electrical insulator).
A non-conductive structure, coating or device that does not transmit sound, heat or electricity (see image)To isolate electrical wires from the pylons supporting them, one often uses glass insulators.