ra·​dio·​ac·​tive | \ ˌrā-dē-ō-ˈak-tiv How to pronounce radioactive (audio) \

Definition of radioactive

1 : of, caused by, or exhibiting radioactivity radioactive isotopes Radon is an odorless, colorless gas that arises naturally from the ground because of the decay of radioactive elements commonly found in rocks and many types of soil. In a chain of radioactive decay, uranium produces radium, which gives off radon, which in turn produces radioactive breakdown products that are harmful if inhaled.— Warren E. Leary
2 : so divisive or controversial as to require avoidance He has been deemed radioactive by most charitable organizations … and organized competition, even local stuff, is largely closed off to him.— Asher Price Almost all women—and therefore men—use a form of birth control at some point in their lives, yet contraception is so politically and legally radioactive that legislators and pharmaceutical companies avoid funding it.— Karen Weise Subsequent polling data show that the quota issue is perhaps the most powerful one in our politics… A House Democratic aide says, "The quota issue is radioactive." The result has been nothing less than panic in the Democratic ranks.— Elizabeth Drew

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Other Words from radioactive

radioactively adverb
Plutonium is the only one of these transuranic elements that can exist a fair amount of time before radioactively decaying into lighter elements. — James Kaler

Examples of radioactive in a Sentence

Uranium and plutonium are radioactive.

Recent Examples on the Web

Ever since the 2011 Fukushima disaster, Japanese authorities have struggled to deal with radioactive water within the destroyed plant. David Grossman, Popular Mechanics, "Would Japan Dump Radioactive Water Into the Pacific Ocean?," 12 Sep. 2019 In 2006, Russian operatives killed former intelligence officer Alexander Litvinenko in London by placing radioactive material in his tea, according to a British investigation. Author: Shane Harris, Ellen Nakashima, Anchorage Daily News, "US got key source out of Russia after election hacking and Trump meeting with Kremlin official," 10 Sep. 2019 Into the Spider-Verse We were introduced to Miles Morales, a scrappy Afro-Latino kid from Brooklyn who turns into Spider-Man after an incident with a radioactive spider. Mehera Bonner And Cady Drell, Marie Claire, "25 Animated Movies Every Adult Should Watch," 5 Sep. 2019 The four-day drills will start Oct. 1 and involve a Chernobyl-like scenario where a nuclear accident at Astravets sends out a radioactive cloud helicopters monitor. Time, "This Lithuanian City Played Host to Filming For HBO's 'Chernobyl.' It's Now Preparing for Its Own Nuclear Radiation Leak," 4 Sep. 2019 Some minerals in tuff contain traces of radioactive potassium-40, which decay like clockwork from the time the minerals were created until the present. Michael Greshko, National Geographic, "'Unprecedented' skull reveals face of human ancestor," 28 Aug. 2019 Washington state officials are worried that the Trump administration wants to reclassify millions of gallons of wastewater from high-level radioactive to low-level, which could reduce cleanup standards and costs., "Wildlife now roam where US once forged its deadliest weapons," 18 Aug. 2019 The official was referring to the 1986 explosion at the Chernobyl nuclear power plant, in the former Soviet republic of Ukraine, which released radioactive airborne contamination for about nine days. Reuters, The Mercury News, "US experts think a recent Russia accident involved nukes," 9 Aug. 2019 After our bus journeyed back to the Exclusion Zone exit checkpoints, we were tested for radioactive dust on devices that looked like subway turnstiles. Dallas News, "Decades after nuclear disaster, tourism is booming at Chernobyl," 18 June 2019

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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Statistics for radioactive

Last Updated

11 Oct 2019

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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 How to pronounce radioactive (audio) \

Kids Definition of radioactive

: caused by or exhibiting radioactivity a radioactive element


ra·​dio·​ac·​tive | \ ˌrād-ē-ō-ˈak-tiv How to pronounce radioactive (audio) \

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

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