Dielectric \Di`e*lec"tric\, n. [Pref. dia- + electric.]

(Elec.) Any substance or medium that transmits the electric force by a process different from conduction, as in the phenomena of induction; a nonconductor. separating a body electrified by induction, from the electrifying body.

Source: Webster's Revised Unabridged Dictionary (1913)