[n] (medicine) the treatment of disease (especially cancer) by exposure to radiation from a radioactive substance
[n] the act of spreading outward from a central source
[n] a radial arrangement of nerve fibers connecting different parts of the brain
[n] the spread of a group of organisms into new habitats
[n] energy that is radiated or transmitted in the form of rays or waves or particles
[n] the spontaneous emission of a stream of particles or electromagnetic rays in nuclear decay
[n] 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"