ra·​dio·​ac·​tive | \ˌrā-dē-ō-ˈak-tiv \

Definition of radioactive 

: of, caused by, or exhibiting radioactivity

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Other Words from radioactive

radioactively adverb

Examples of radioactive in a Sentence

Uranium and plutonium are radioactive.

Recent Examples on the Web

Bay Area & StatePittsburg residents fear city dump tainted with radioactive waste... J.k. Dineen,, "Building paused as questions linger over contamination at SF’s Hunters Point," 28 June 2018 Microorganisms flourish at the bottom of the cold sea and in the vents of boiling hot springs; bacteria can even survive in radioactive waste. Jason Pontin, WIRED, "The 19th-Century Crank Who Tried to Tell Us About the Microbiome," 15 June 2018 In the future, the MIT team hopes to build a stronger, more intelligent version of this robot that can be used for tasks such as medical procedures or cleaning up radioactive waste. Sarah Gibbens, National Geographic, "These Soft, Magnetic Robots May One Day Crawl Inside Your Body," 13 June 2018 Such a plant would have produced nearly 600 full-time jobs in the region, though preparing the radioactive waste for disposal is also expected to create 400 jobs through 2040. Megan Geuss, Ars Technica, "Plan to make fuel from weapons-grade plutonium oxides dead on arrival," 13 May 2018 Waste Control Specialists owns a facility that already stores low-level radioactive waste and wants to expand. Rob Nikolewski,, "U.S. House passes bill to restart Yucca Mountain and look for interim sites for nuclear waste," 10 May 2018 Different water supplies worldwide also have their own radioactive signatures and help geolocate where a person may have spent part of their lifetime. Kyle Mizokami, Popular Mechanics, "How U.S. Investigators Identify Korean War Dead Using DNA, Corn, and Water," 19 Sep. 2018 ANDREI LUGOVOI Accused of poisoning and killing ex-KGB officer Alexander Litvinenko in 2006 with radioactive tea in London, Lugovoi, a former KGB officer, parlayed his newfound fame into a political career. Greg Norman, Fox News, "Russians accused of crimes abroad finding fame in their homeland," 13 Sep. 2018 He was served tea spiked with Polonium 210, a radioactive isotope. Ellen Barry, New York Times, "Dawn Sturgess, British Woman Poisoned by Novichok, Dies," 8 July 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'radioactive.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of radioactive

1898, in the meaning defined above

History and Etymology for radioactive

International Scientific Vocabulary

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Last Updated

6 Dec 2018

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Time Traveler for radioactive

The first known use of radioactive was in 1898

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English Language Learners Definition of radioactive

: having or producing a powerful and dangerous form of energy (called radiation)


ra·​dio·​ac·​tive | \ˌrā-dē-ō-ˈak-tiv \

Kids Definition of radioactive

: caused by or exhibiting radioactivity a radioactive element


ra·​dio·​ac·​tive | \ˌrād-ē-ō-ˈak-tiv \

Medical Definition of radioactive 

: of, caused by, or exhibiting radioactivity radioactive isotopes

Other Words from radioactive

radioactively adverb

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More from Merriam-Webster on radioactive

Spanish Central: Translation of radioactive

Nglish: Translation of radioactive for Spanish Speakers

Britannica English: Translation of radioactive for Arabic Speakers

Comments on radioactive

What made you want to look up radioactive? Please tell us where you read or heard it (including the quote, if possible).


to make faulty or ineffective

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