insulator

American  

[in-suh-ley-ter, ins-yuh-] / ˈɪn səˌleɪ tər, ˈɪns yə- /

noun

1. Electricity.

   1. a material of such low conductivity that the flow of current through it is negligible.

   2. insulating material, often glass or porcelain, in a unit form designed so as to support a charged conductor and electrically isolate it.

2. a person or thing that insulates.

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insulator British  

/ ˈɪnsjʊˌleɪtə /

noun

1. any material or device that insulates, esp a material with a very low electrical conductivity or thermal conductivity or something made of such a material

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insulator Scientific  

/ ĭn′sə-lā′tər /

1. A material or an object that does not easily allow heat, electricity, light, or sound to pass through it. Air, cloth and rubber are good electrical insulators; feathers and wool make good thermal insulators.

2. Compare conductor

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insulator Cultural  

1. A material that does not easily transmit energy, such as electric current (see also current) or heat. Materials such as wood, plastic, and ceramics are insulators. Fiberglass is an example of a heat insulator. (Compare conductor.)

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Other Word Forms

• noninsulator noun

Etymology

Origin of insulator

First recorded in 1795–1805; insulate + -or ²

Explanation

Any material that keeps energy such as electricity, heat, or cold from easily transferring through is an insulator. Wood, plastic, rubber, and glass are good insulators. Swiss cheese...not so much. The word insulator comes from the Latin root insulātus, which means "like an island." If your house is built out of good insulators, you might enjoy an island of warmth inside it even during cold winter nights. The opposite of insulator is conductor: a material that easily transmits heat or electricity.

Example Sentences

As the density dropped, the flow stopped entirely, and the system became an insulator.

From Science Daily • Feb. 5, 2026

The inquest heard the company had since brought in changes, stopped using that type of insulator and was rolling out a programme to replace them at about 8,000 locations.

From BBC • Jan. 29, 2026

A typical double-hung window—even a double-glazed one—is so leaky, and such a poor insulator, that if your home were a bucket, your windows are effectively holes in it.

From The Wall Street Journal • Nov. 21, 2025

Instead of acting like a metal, it behaves as an insulator.

From Science Daily • Nov. 17, 2025

Human skin can be a relatively good insulator, if it is dry.

From "Escape from Camp 14: One Man's Remarkable Odyssey from North Korea to Freedom in the West" by Blaine Harden