plutonium
noun
plu·to·ni·um
plü-ˈtō-nē-əm 
: a radioactive metallic element similar chemically to uranium that is formed as the isotope 239 by decay of neptunium and found in minute quantities in pitchblende, that undergoes slow disintegration with the emission of an alpha particle to form uranium 235, and that is fissionable with slow neutrons to yield atomic energy see Chemical Elements Table
Examples of plutonium in a Sentence
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The energy department said being selected to receive the plutonium could help companies secure faster approval for a Nuclear Regulatory Commission license, which is required to operate a nuclear facility, reported Financial Times.
—
Prabhat Ranjan Mishra, Interesting Engineering, 23 Oct. 2025
In 1943, the area just to its north was selected as the location of the Manhattan Project’s first large-scale plutonium-production reactor, which made the plutonium in the Fat Man bomb dropped on Nagasaki.
—Molly Fischer, New Yorker, 20 Oct. 2025
The former Rocky Flats weapons plant, which produced plutonium triggers for nuclear bombs, drew thousands of protesters for years to the site north of Denver, including such prominent activists as Daniel Ellsberg and Beat poet Allen Ginsberg.
—Judith Kohler, Denver Post, 13 Oct. 2025
The agreement, ratified in 2011, required both nations to dispose of 34 tons of weapons-grade plutonium.
—Amanda Castro, MSNBC Newsweek, 8 Oct. 2025
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Prabhat Ranjan Mishra, Interesting Engineering, 23 Oct. 2025
In 1943, the area just to its north was selected as the location of the Manhattan Project’s first large-scale plutonium-production reactor, which made the plutonium in the Fat Man bomb dropped on Nagasaki.
—Molly Fischer, New Yorker, 20 Oct. 2025
The former Rocky Flats weapons plant, which produced plutonium triggers for nuclear bombs, drew thousands of protesters for years to the site north of Denver, including such prominent activists as Daniel Ellsberg and Beat poet Allen Ginsberg.
—Judith Kohler, Denver Post, 13 Oct. 2025
The agreement, ratified in 2011, required both nations to dispose of 34 tons of weapons-grade plutonium.
—Amanda Castro, MSNBC Newsweek, 8 Oct. 2025
See All Example Sentences for plutonium
Cite this Entry
“Plutonium.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/plutonium. Accessed 31 Oct. 2025.
Copy CitationKids Definition
plutonium
noun
plu·to·ni·um
plü-ˈtō-nē-əm
: a radioactive metallic element that is formed by decay of neptunium and found in minute quantities in pitchblende and that produces atomic energy by fission see element
Medical Definition
plutonium
noun
plu·to·ni·um
plü-ˈtō-nē-əm
: a radioactive metallic element similar chemically to uranium that is formed as the isotope 239 by decay of neptunium and found in minute quantities in pitchblende, that undergoes slow disintegration with the emission of an alpha particle to form uranium 235, and that is fissionable with slow neutrons to yield atomic energy
—symbol Pu
see Chemical Elements Table
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