free radical

free radical   n.  An atom or group of atoms that has at least one unpaired electron and is therefore unstable and highly reactive. In animal tissues, free radicals can damage cells and are believed to accelerate the progression of cancer, cardiovascular disease, and age-related diseases.

Main Entry: free radical
Function: noun
: an especially reactive atom or group of atoms that has one or more unpaired electrons; especially : one that isproduced in the body by natural biological processes or introduced from outside (as in tobacco smoke, toxins, or pollutants) and that can damage cells, proteins, and DNA by altering their chemicalstructure

free radical n.

1. An uncharged atom or group of atoms having at least one unpaired electron, which makes it highly reactive.

2. An organic compound having some unpaired valence electrons; a normal byproduct of oxidation reactions in metabolism.