Meaning of free radical

free' rad'ical

Pronunciation: [key]
— Chem., Biochem. Chem.,Biochem.
  1. an atom or molecule that bears an unpaired electron and is extremely reactive, capable of engaging in rapid chain reactions that destabilize other molecules and generate many more free radicals: in the body, deactivated by antioxidants, uric acid, and certain enzyme activities. Cf. diradical.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.