Insulator

[Little_Girl]

The substance or body that insulates; a nonconductor.

[Sonia]

A glass or porcelain device used on powerlines used to keep electricity on the line instead of going straight to ground.

[Tracie Lynn]

A material that is a very poor conductor of electricity. The insulating material is usually a ceramic or fiberglass when used in the transmission line and is designed to support a conductor physically and to separate it electrically from other conductors and supporting material.

[exinilu]

A substance which does not readily allow the passage of heat or sound.