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

Diminutive antibodies can also be fused to radioactive or fluorescent tracers to illuminate tumors or even guide surgery. Mitch Leslie, Science | AAAS, "Mini-antibodies discovered in sharks and camels could lead to drugs for cancer and other diseases," 10 May 2018 Idaho State University was fined last week for losing a small amount of radioactive, weapons-grade plutonium that is too small to make a nuclear bomb, but could be used in a dirty bomb, according to a regulatory commission. Fox News, "Idaho State University loses weapons-grade plutonium capable of making a dirty bomb," 8 May 2018 The amount is too small to make a nuclear bomb, agency spokesman Victor Dricks said Friday, but could be used to make a dirty bomb to spread radioactive contamination. CBS News, "Idaho State University faces fine for losing plutonium used to make dirty bombs," 8 May 2018 Sinema’s campaign has had to weigh what to do about politically radioactive donors in the recent past. Ronald J. Hansen, azcentral, "Kyrsten Sinema took thousands from California congressman accused of molesting girl," 7 May 2018 The resulting 56 million gallons of radioactive and hazardous wastes are stored in 177 underground tanks, many of which are leaking. Nicholas K. Geranios, The Seattle Times, "Feds demand proof that steel for giant nuclear-waste treatment plant in Washington state is safe," 16 Mar. 2018 The skyline in Long Island, New York looked positively radioactive. Diana Bruk, Country Living, "23 Unbelievably Stunning Photos of the Northern Lights From Tuesday's Solar Storm," 18 Mar. 2015 In Hawaii and other parts of the United States, there has been, for example, a spike in sales of potassium iodide, a drug that can block the thyroid gland from absorbing radioactive iodine released in a nuclear attack. Clyde Haberman, New York Times, "‘This Is Not a Drill’: The Growing Threat of Nuclear Annihilation," 13 May 2018 In addition, smokers also tend to have worsening eye disease after radioactive iodine. Andrea K. Mcdaniels,, "What is Graves' disease? A MedStar endocrinologist explains," 5 Apr. 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

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Last Updated

11 Oct 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).


evasion of direct action or statement

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