a material such as glass or porcelain with negligible electrical or thermal conductivity
"The engineer selected high-quality porcelain as the dielectric insulator to prevent any electrical leakage in the power transmission line."
An electrically insulating or nonconducting material considered for its electric susceptibility, i.e. its property of polarization when exposed to an external electric field.
"The engineer selected a ceramic dielectric because its high polarizability allowed the capacitor to store significantly more charge than standard plastic alternatives."
insulating
"The engineer selected a ceramic dielectric to ensure the power lines remained electrically insulated from the rain."