Source : Webster's Revised Unabridged Dictionary (1913)

Nonconductor \Non`con*duct"or\, n. (Physics)
   A substance which does not conduct, that is, convey or
   transmit, heat, electricity, sound, vibration, or the like,
   or which transmits them with difficulty; an insulator; as,
   wool is a nonconductor of heat; glass and dry wood are
   nonconductors of electricity.

Source : WordNet®

nonconductor
     n : a material such as glass or porcelain with negligible
         electrical or thermal conductivity [syn: {insulator}, {dielectric}]
         [ant: {conductor}]