Refers to a material that conducts heat or electricity. Common in physics and engineering contexts.
Copper is a good conductor of electricity.
This material is used as a conductor of heat.
導体 conducts electricity well, while 半導体 has conductivity only between that of a conductor and an insulator.
導体 is a Sino-Japanese compound of 導 (guide, conduct) and 体 (body, substance), literally 'conducting body'.