dielectric

/D IH0 L EH1 K T R IH0 K/
noun
  1. 1

    An electrically insulating or nonconducting material considered for its electric susceptibility, i.e. its property of polarization when exposed to an external electric field.

Synonyms

adjective
  1. 1

    (electrically) insulating

Source: https://en.wiktionary.org/wiki/dielectric