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free radical

noun, Chemistry, Biochemistry.
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.
Compare diradical.
Origin of free radical
First recorded in 1895-1900 Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for free radical
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  • I always thought a free radical was a political bomb thrower out of jail.

    The Egyptian Cat Mystery Harold Leland Goodwin
British Dictionary definitions for free radical

free radical

an atom or group of atoms containing at least one unpaired electron and existing for a brief period of time before reacting to produce a stable molecule Sometimes shortened to radical Compare group (sense 10)
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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free radical in Medicine

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.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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free radical in Science
free radical  
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.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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