radioactive
Americanadjective
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Physics, Chemistry. of, relating to, exhibiting, or caused by radioactivity.
A pressing issue in post-Soviet Russia is safe long-term storage of radioactive waste, from both military and civilian applications.
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relating to or being a person, topic, or matter that is likely to provoke intense negative reactions or disagreement.
The option of raising taxes to fund these expenditures is a politically radioactive approach that a majority of state policymakers have avoided.
adjective
Usage
What does radioactive mean? Radioactive describes something that exhibits or is caused by radioactivity. If something is radioactive, it emits radiation, which usually takes the form of electromagnetic waves or fast-moving elementary particles, such as protons or neutrons. While low doses of radiation are usually harmless, being exposed to large amounts of radiation will most likely kill you. For this reason, highly radioactive materials are often considered very dangerous and will only be handled by experts. Example: The radioactive waste produced by nuclear power plants can damage the environment.
Other Word Forms
Etymology
Origin of radioactive
Explanation
When an object gives off a certain kind of energy, like the sun or an x-ray machine, it can be described as radioactive. The adjective radioactive is a scientific term for a particular type of energy-emitting substance or thing. Radioactive energy, or radiation, is made up of active particles or electromagnetic waves. Nuclear waste is radioactive, but so are more ordinary things, like cell phones and the food we eat. The French word for it is radio-actif, which was invented by Pierre and Marie Curie, who combined radiationem, Latin for "a shining" with actif, French for "active."
Vocabulary lists containing radioactive
Spider-Man's Word Web
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Just Do It: Act
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List 4
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
“I think he’s dangerously tactless in a radioactive topic” and “should exercise more caution,” Steven Pinker, author and Harvard University evolutionary psychologist, says of Cofnas’s rhetoric on genetics’ role in intelligence.
From The Wall Street Journal ● Aug. 21, 2026
That radioactive spider that transformed Peter Parker into Spider-Man could have bitten the class moron just as easily.
From Salon ● Aug. 16, 2026
Any comic book fan knows that Spider-Man's secret identity is Peter Parker, a science nerd who gained superhero powers after being bitten by a radioactive spider.
From BBC ● Jul. 31, 2026
Separating and purifying the elements from mineral deposits often requires toxic chemicals, while radioactive substances are frequently present in the same geological formations.
From Science Daily ● Jul. 24, 2026
But a properly functioning coal-burning plant spreads radioactive lead, uranium, radon, polonium, and thorium every day.
From "Meltdown" by Deirdre Langeland
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
