ETYM Old Eng. sheld, scheld, AS. scield, scild, sceld, scyld; akin to OS. scild, OFries. skeld, Dutch and German schild, Old High Germ. scilt, Icel. skjöldr, Swed. sköld, Dan. skiold, Goth. skildus; of uncertain origin. Related to Sheldrake.
In geology, alternate name for craton, the ancient core of a continent.
1. A protective structure or device (usually metal).
2. Armor carried on the arm to intercept blows; SYN. buckler.

To protect, hide, or conceal from danger or harm; SYN. screen.

In technology, any material used to reduce the amount of radiation (electrostatic, electromagnetic, heat, nuclear) reaching from one region of space to another, or any material used as a protection against falling debris, as in tunneling.
Electrical conductors are used for electrostatic shields, soft iron for electromagnetic shields, and poor conductors of heat for heat shields. Heavy materials such as lead and concrete are used for protection against X-rays and nuclear radiation. See also biological shield and heat shield.