Materials that do not conduct electricity well are called insulators.

Here are some other terms that are sometimes used:

* Non-conductors: This is a synonym for insulators.

* Dielectrics: This term is often used in the context of capacitors, where the material is used to store electrical energy.

It's important to note that no material is a perfect insulator. Even the best insulators will conduct a tiny amount of electricity under high enough voltage.