free radical
noun /ˌfriː ˈrædɪkl/
/ˌfriː ˈrædɪkl/
(chemistry)- an atom or group of atoms that has an electron that is not part of a pair, causing it to take part easily in chemical reactions. Free radicals in the body are thought to be one of the causes of diseases such as cancer. see also antioxidant (1)