[ rey-dee-oh-ak-tiv ]
See synonyms for radioactive on
  1. Physics, Chemistry. of, relating to, exhibiting, or caused by radioactivity: A pressing issue in post-Soviet Russia is safe long-term storage of radioactive waste, from both military and civilian applications.

  2. relating to or being a person, topic, or matter that is likely to provoke intense negative reactions or disagreement: The option of raising taxes to fund these expenditures is a politically radioactive approach that a majority of state policymakers have avoided.

Origin of radioactive

First recorded in 1895–1900; radio- + active

Other words from radioactive

  • ra·di·o·ac·tive·ly, adverb
  • non·ra·di·o·ac·tive, adjective
  • un·ra·di·o·ac·tive, adjective

Words Nearby radioactive Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use radioactive in a sentence

British Dictionary definitions for radioactive


/ (ˌreɪdɪəʊˈæktɪv) /

  1. exhibiting, using, or concerned with radioactivity

Derived forms of radioactive

  • radioactively, adverb

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

Cultural definitions for radioactive


A descriptive term for a material made up of atoms in which radioactivity occurs.

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.