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

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

Soon after, Tarek was scheduled for surgeries and radioactive iodine therapy to beat both forms of cancer. Taylor Mead, House Beautiful, "Flip or Flop Star Tarek El Moussa Is Officially Cancer Free Six Years After His Diagnosis," 18 Mar. 2019 Dua Lipa wearing a strappy one-shoulder dress covered in radioactive green graphics in her native London, England. Vogue, "The 19 Best Fashion Instagrams of the Week: Cardi B, Rick Owens, and More," 9 Mar. 2019 Enough to destroy entire coastal cities and cause further devastation inland by triggering artificial tsunamis, laden with radioactive fallout. Kyle Mizokami, Popular Mechanics, "Russia’s Nuclear Tsunami Apocalypse Torpedo is Named 'Poseidon'," 24 July 2018 Park officials became aware of the radioactive buckets, located near a taxidermy exhibit, last year. David Grossman, Popular Mechanics, "The Grand Canyon's Museum Has Reportedly Been Exposing Tourists to Uranium for 18 Years," 19 Feb. 2019 The event overwhelmed the defenses of reactors at the Fukushima Daiichi site, causing widespread damage and radioactive releases, raising questions earlier seismic assessments. Timothy Puko, WSJ, "Nuclear Power Regulators Scale Back Draft Safety Rule," 24 Jan. 2019 The fire is adjacent to another landfill, which contains radioactive waste from the Manhattan Project. Naomi Fry, The New Yorker, "Scott Pruitt’s Dirty Politics," 3 Apr. 2017 As if a runaway train and a Norseman derailment weren’t enough, on Nov. 6—a day after the BHP crash—coal and copper giant Glencore announced that a portion of its cobalt is radioactive. Nathaniel Taplin, WSJ, "Strange Tales, Fantastic Journeys in the Wild World of Mining," 16 Nov. 2018 The Navy determined in 1974 that neither Prinz Eugen nor the oil inside the wreck is still radioactive. Kyle Mizokami, Popular Mechanics, "How the U.S. Is Recovering Oil from a Nuked Warship," 17 Sep. 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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Statistics for radioactive

Last Updated

29 Mar 2019

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Time Traveler for radioactive

The first known use of radioactive was in 1898

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More Definitions for radioactive



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

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).


an enemy or opponent

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