An Etymological Dictionary of Astronomy and Astrophysics

1. A material or an object that does not easily allow heat, electricity, light, or sound to pass through it.
   

2. Electricity: A material, such as glass or porcelain, that opposes a very high resistance to the passage of an electric current so that the flow of current through it is negligible; a nonconductor.
   

3. One who, or that which, insulates.

Etymology (EN): Agent noun from → insulate + → -or.

Etymology (PE): Âyeq, loan from Ar.