What is "heat shield"

n. (context space science English) A shield designed of a substance that absorbs excessive heat from an outside source by either dissipating, reflecting or simply absorbing the heat.

n. a protective covering that protects a spacecraft from overheating on re-entry

A heat shield is designed to shield a substance from absorbing excessive heat from an outside source by either dissipating, reflecting or simply absorbing the heat. It is often used as a form of exhaust heat management.