radioactive

adjective

ra·​dio·​ac·​tive ˌrā-dē-ō-ˈak-tiv How to pronounce radioactive (audio)
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
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 The production asks us to commune with Morrison’s radioactive words and insights, to reckon with the story in a public forum. Charles McNulty, Los Angeles Times, 14 Sep. 2023 For example, smoke detectors use a radioactive source to detect smoke in the air. WIRED, 8 Sep. 2023 Named for the region of the Sahara Desert in Algeria where it was discovered in 2020, Erg Chech 002 was found to contain higher levels than expected of a radioactive isotope known as aluminum-26. Eric Lagatta, USA TODAY, 7 Sep. 2023 The Wall Street Journal on Sept. 4, 2023, removed from its website an article incorrectly dated Aug. 24, 2023, which reported that several countries had detected radioactive contamination in Japanese food exports. WSJ, 4 Sep. 2023 The European environment received a large pulse of radioactive cesium contamination following the Chernobyl power plant accident 37 years ago, mostly from cesium-137. Tim Newcomb, Popular Mechanics, 1 Sep. 2023 Four top Japanese government ministers, including Prime Minister Fumio Kishida, ate sashimi from Fukushima this week, seeking to dispel safety concerns about fish from the region after the release of treated radioactive water from the Fukushima nuclear power plant. Julia Mio Inuma, Washington Post, 31 Aug. 2023 Alistair Fuller/Associated Press Former intelligence operatives In 2006, Russian defector Alexander Litvinenko, a former agent for the KGB and its post-Soviet successor agency, the FSB, felt violently ill in London after drinking tea laced with radioactive polonium-210, dying three weeks later. Dasha Litvinova, BostonGlobe.com, 25 Aug. 2023 Steven Ferdman—Getty Images Japan began releasing more than 1 million metric tons of radioactive water from a wrecked nuclear power plant on Thursday, prompting widespread concerns over contamination and safety. Chloe Taylor, Fortune, 24 Aug. 2023 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'radioactive.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

Etymology

International Scientific Vocabulary

First Known Use

1898, in the meaning defined at sense 1

Time Traveler
The first known use of radioactive was in 1898

Dictionary Entries Near radioactive

Cite this Entry

“Radioactive.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/radioactive. Accessed 29 Sep. 2023.

Kids Definition

radioactive

adjective
ra·​dio·​ac·​tive ˌrād-ē-ō-ˈak-tiv How to pronounce radioactive (audio)
: of, caused by, or exhibiting radioactivity
radioactively adverb

Medical Definition

radioactive

adjective
ra·​dio·​ac·​tive ˌrād-ē-ō-ˈak-tiv How to pronounce radioactive (audio)
: of, caused by, or exhibiting radioactivity
radioactive isotopes
radioactively adverb

More from Merriam-Webster on radioactive

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