1
: a splitting or breaking up into parts
2
: reproduction by spontaneous division of the body into two or more parts each of which grows into a complete organism
3
: the splitting of an atomic nucleus resulting in the release of large amounts of energy
fissioned; fissioning; fissions
: to undergo fission
: to cause to undergo fission
Examples of fission in a Sentence
Recent Examples on the Web
Eric Berger, ArsTechnica, 12 June 2025
Here, the margins of the prints often bleed into one another, disrupting distinctions between past and present, public and private, parent and offspring, and fission and fusion, echoing the dichotomies alluded to in My Birth.
—Jessica Simmons-Reid, Artforum, 1 June 2025
Washington Post, 28 Apr. 2022
The point is that by analyzing the array of radioactive fission products – those that can be captured and analyzed – nuclear forensic specialists can start to figure out if the atoms that fissioned were U-235, Pu-239, or (in some cases) U-238.
—Andrew Karam, Popular Mechanics, 7 Jan. 2016
See All Example Sentences for fission
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Noun
Nuclear electric propulsion converts heat from a fission reactor to electrical power, like a power plant on Earth, and then uses this energy to produce thrust by accelerating an ionized propellant, such as xenon.
—Eric Berger, ArsTechnica, 12 June 2025
Here, the margins of the prints often bleed into one another, disrupting distinctions between past and present, public and private, parent and offspring, and fission and fusion, echoing the dichotomies alluded to in My Birth.
—Jessica Simmons-Reid, Artforum, 1 June 2025
Verb
Most atoms do not fission, but the isotopes of certain elements, such as uranium-235, are fissile.
—Washington Post, 28 Apr. 2022
The point is that by analyzing the array of radioactive fission products – those that can be captured and analyzed – nuclear forensic specialists can start to figure out if the atoms that fissioned were U-235, Pu-239, or (in some cases) U-238.
—Andrew Karam, Popular Mechanics, 7 Jan. 2016
See All Example Sentences for fission
Cite this Entry
“Fission.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/fission. Accessed 29 Jun. 2025.
Copy CitationKids Definition
fission
1 of 2 noun
fis·sion
ˈfish-ən 
also ˈfizh-
1
: a splitting or breaking up into parts
2
: a method of reproduction in which a living cell or body divides into two or more parts each of which grows into a whole new individual
3
: the splitting of an atomic nucleus resulting in the release of large amounts of energy
fission
2 of 2 verb
fissioned; fissioning
ˈfish-(ə-)niŋ,
ˈfizh-
: to go through or cause to go through fission
Medical Definition
fission
noun
fis·sion
ˈfish-ən also ˈfizh-
1
: a method of reproduction in which a living cell or body divides into two or more parts each of which grows into a whole new individual
2
a
b
: the splitting of an atomic nucleus resulting in the release of large amounts of energy
called also nuclear fission
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