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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Starring Chris Pratt as Mario, Charlie Day as Luigi, and Jack Black as Bowser, the new take on the Mario movie packed more (intentionally) comedic weight and was kid-friendly, weapons-grade plutonium at the box office.
—
Christopher Cruz, Rolling Stone, 5 Apr. 2026
The bombs’ nuclear warheads weren’t armed, but their plutonium cores were.
—Encyclopedia Britannica, 3 Apr. 2026
These and other features, including extensive air handling equipment, are designed to keep highly radioactive materials such as uranium and plutonium trapped inside the dome, according to multiple experts.
—Tamara Qiblawi, CNN Money, 1 Apr. 2026
Despite these changes, experts have long warned that the original design could allow the production of weapons-grade plutonium if restored.
—Sujita Sinha, Interesting Engineering, 30 Mar. 2026
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Christopher Cruz, Rolling Stone, 5 Apr. 2026
The bombs’ nuclear warheads weren’t armed, but their plutonium cores were.
—Encyclopedia Britannica, 3 Apr. 2026
These and other features, including extensive air handling equipment, are designed to keep highly radioactive materials such as uranium and plutonium trapped inside the dome, according to multiple experts.
—Tamara Qiblawi, CNN Money, 1 Apr. 2026
Despite these changes, experts have long warned that the original design could allow the production of weapons-grade plutonium if restored.
—Sujita Sinha, Interesting Engineering, 30 Mar. 2026
See All Example Sentences for plutonium
Cite this Entry
“Plutonium.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/plutonium. Accessed 14 Apr. 2026.
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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