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 By 2010, a growing underground fire about 1,000 feet from the radioactive material was discovered. —Catie Edmondson, New York Times, 6 Apr. 2024 An accident involving military equipment and ordnance could damage the systems needed to cool the reactors, and could lead to a leak of radioactive material. —Nataliya Gumenyuk, The Atlantic, 6 Mar. 2024 None of these fragments, ESA said, contain toxic or radioactive substances. —John Tufts, The Indianapolis Star, 23 Feb. 2024 Clues pointing to the radioactive waste emerged in the process of sorting through this DDT history. —Rosanna Xia, Los Angeles Times, 21 Feb. 2024 Godzilla: Final Wars (2004) Godzilla: Final Wars was conceived as a 50th birthday bash for everyone’s favorite radioactive threat turned fearsome protector of mankind. —Katie Rife, EW.com, 28 Mar. 2024 In the case of radiation leakage, radioactive iodine is one of the materials that may be released into the environment and can be absorbed and stored in the thyroid, which relies on iodine for hormone synthesis. —Kylie Martin, Detroit Free Press, 28 Mar. 2024 Why does a gamer slay that giant, radioactive scorpion? —Ian Walker |, Popular Science, 27 Mar. 2024 These medications hit cancer cells directly via radioactive isotopes that target molecules like antibodies and peptides. —Bruce Gil, Quartz, 19 Mar. 2024

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

radioactivate

radioactive

radioactive chain

See More Nearby Entries 

Cite this Entry

“Radioactive.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/radioactive. Accessed 19 Apr. 2024.

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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

Nglish: Translation of radioactive for Spanish Speakers

Britannica English: Translation of radioactive for Arabic Speakers

Last Updated: - Updated example sentences
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