(1)   (medicine) the treatment of disease (especially cancer) by exposure to a radioactive substance
(2)   The act of spreading outward from a central source
(3)   A radial arrangement of nerve fibers connecting different parts of the brain
(4)   The spread of a group of organisms into new habitats
(5)   Energy that is radiated or transmitted in the form of rays or waves or particles
(6)   The spontaneous emission of a stream of particles or electromagnetic rays in nuclear decay
(7)   Syndrome resulting from exposure to ionizing radiation (e.g., exposure to radioactive chemicals or to nuclear explosions); low doses cause diarrhea and nausea and vomiting and sometimes loss of hair; greater exposure can cause sterility and cataracts and some forms of cancer and other diseases; severe exposure can cause death within hours
"He was suffering from radiation"


  1. The shooting forth of anything from a point or surface, like the diverging rays of light; as, the radiation of heat.
  2. The process of radiating waves or particles.
  3. The transfer of energy via radiation (as opposed to convection or conduction)
  4. Radioactive energy