Insulator
A device made of an electrically insulating material used to separate or support conductors.
Also, a material that is a poor conductor (as of electricity or heat) [Merriam-Webster Online Dictionary].
Any substances that block or retard the flow of electrical or thermal currents.
Although an electrical insulator is ordinarily thought of as a non-conducting material, it is better described as a poor conductor or a substance of high resistance to the flow of electric current. In this regard, different insulating and conducting materials are compared with each other by means of a material constant known as resistivity. Electrical insulators hold conductors in position, separating them from one another and surrounding structures. They form a barrier between energized parts of an electric circuit and confine the flow of current to wires or other conducting paths as desired [Encyclopaedia Britannica].
A material in which electric current does not flow freely. The atoms of the insulator have tightly bound electrons that cannot readily move. Other materials-semiconductors and conductors-conduct electric current more easily. The property that distinguishes an insulator is its resistivity; insulators have higher resistivity than semiconductors or conductors. The most common examples are non-metals [Waygood, p.41].
Insulator. Merriam-Webster Online Dictionary. Retrieved from: https://www.merriam-webster.com/dictionary/insulator
Insulator. Encyclopedia Britannica. Retrieved from: https://www.britannica.com/science/insulator
Waygood, A. (2013). An Introduction to Electrical Science. Abingdon-on-Thames: Routledge.