Definition & Meaning of "radiation"

the act of spreading outward from a central source

(medicine) the treatment of disease (especially cancer) by exposure to a radioactive substance

a radial arrangement of nerve fibers connecting different parts of the brain

the spread of a group of organisms into new habitats

the spontaneous emission of a stream of particles or electromagnetic rays in nuclear decay

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