undershield

Science Dictionary
shield   (shēld)  Pronunciation Key 
  1. A wall or housing of an absorbing material, such as concrete or lead, built around a nuclear reactor to prevent the escape of radiation.

  2. A structure or arrangement of metal plates or mesh designed to protect a piece of electronic equipment from electrostatic or magnetic interference.

  3. A large geographic area where rocks of a continent's craton (the ancient, relatively undisturbed portion of a continental plate) are visible at the surface. A shield is often surrounded by platforms covered with sediment.


The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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