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When scientists first used fissile back in the 1600s, the notion of splitting an atom would have seemed far-fetched indeed. At that time, people thought that atoms were the smallest particles of matter that existed and therefore could not be split. Fissile (which can be traced back to the Latin verb findere, meaning "to split") was used in reference to things like rocks. When we hear about fissile materials today, the reference is usually to nuclear fission: the splitting of an atomic nucleus that releases a huge amount of energy. But there is still a place in our language for the original sense of fissile (and for the noun fissility, meaning "the quality of being fissile"). A geologist or builder, for example, might describe slate as being fissile, as it splits readily into thin slabs.
Examples of fissile in a Sentence
Llewellyn King, Forbes.com, 27 Apr. 2025
The key characteristic of this posture was the separation of the fissile and non-fissile parts of nuclear weapons, as well as the separation of weapons from their delivery systems.
—Gaurav Kampani, Foreign Affairs, 16 June 2017
One way for North Korea to boost its nuclear stockpile is to ramp up production of lower-yield tactical weapons that require less fissile material.
—Time, 9 Jan. 2023
The new system retains the latter’s ability to burn the widest possible range of fuels — including not just spent nuclear fuel, but also the ordinarily non-fissile uranium-238.
—M. Mitchell Waldrop, Discover Magazine, 26 Feb. 2019
See All Example Sentences for fissile
Cite this Entry
“Fissile.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/fissile. Accessed 28 May. 2025.
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