a radioactive isotope, usually artificially produced: used in physical and biological research, therapeutics, etc.

1940–45; radio- + isotope

radioisotopic [rey-dee-oh-ahy-suh-top-ik] , adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
radioisotope (ˌreɪdɪəʊˈaɪsətəʊp)
an isotope that is radioactive

Collins English Dictionary - Complete & Unabridged 10th Edition
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American Heritage
Medical Dictionary

radioisotope ra·di·o·i·so·tope (rā'dē-ō-ī'sə-tōp')
A naturally or artificially produced radioactive isotope.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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American Heritage
Science Dictionary
radioisotope   (rā'dē-ō-ī'sə-tōp')  Pronunciation Key 
A radioactive isotope of a chemical element. Carbon 14 and radon 222 are examples of naturally occurring radioactive isotopes.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Britannica


any of several species of the same chemical element with different masses whose nuclei are unstable and dissipate excess energy by spontaneously emitting radiation in the form of alpha, beta, and gamma rays.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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