Taber’s Cyclopedic Medical Dictionary Online + App from F.A. Davis and Unbound Medicine. Find 65,000 medical and nursing definitions. Download to iPhone, iPad, and Android. Explore these free sample topics:
-- The first section of this topic is shown below --
1. A cover or barrier; any layer or structure that limits exposure to a potentially toxic agent, such as a source of body fluids or radiation.
2. In biology, a protective plate or hard outer covering.