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[fis-uh l] /ˈfɪs əl/
capable of being split or divided; cleavable.
  1. fissionable.
  2. (of a nuclide) capable of undergoing fission induced by low-energy neutrons, as uranium 233 and 235.
1655-65; < Latin fissilis, equivalent to fiss(us) (see fissi-) + -ilis -ile
Related forms
fissility, noun
nonfissile, adjective
nonfissility, noun
unfissile, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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Examples for fissile
  • At some point, they're going to have enough in the way of fissile material out of which to make a weapon.
  • As soon as uranium fission was considered for nuclear weapons, it was understood that the fissile isotope was the relevant one.
  • Breeders actually breed fissile isotopes, which are useful as reactor fuel, from neutrons and fertile isotopes.
  • If reactors can be build using other fissile materials it may be possible.
  • Without a treaty to prohibit the use of fissile material for weapons production the world will not get to zero.
  • We'll start by seeking a global ban on the production of fissile material for weapons.
  • fissile material shall mean a material containing any of the fissile nuclides.
  • AS fissile materials are being created and destroyed in a nuclear reactor, tracking their inventory can be a tricky business.
  • It is intended that this guide be applied to facilities which process, handle, or store fissile materials.
  • Total uncertainties for the benchmark cores are caused primarily by those for each of the fissile isotopes.
British Dictionary definitions for fissile


(Brit) capable of undergoing nuclear fission as a result of the impact of slow neutrons
(US & Canadian) another word for fissionable
tending to split or capable of being split
Derived Forms
fissility (fɪˈsɪlɪtɪ) noun
Word Origin
C17: from Latin fissilis, from fissus split; see fissi-
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for fissile
1660s, from L. fissilis, from findere (see fissure).
Online Etymology Dictionary, © 2010 Douglas Harper
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