nonconductor n a material such as glass or porcelain with negligible electrical or thermal conductivity Usage(s) Lem Lemnitzer moved like a nonconductor. Mica, which laymen know as isinglass, is mainly used in peacetime as a nonconductor for electrical equipment. Aluminum electrical wiring oxidizes on contact with moisture and turns into a nonconductor. Synonym(s) insulator dielectric Antonym(s) conductor