[fis-uh l]
  1. capable of being split or divided; cleavable.
  2. Physics.
    1. fissionable.
    2. (of a nuclide) capable of undergoing fission induced by low-energy neutrons, as uranium 233 and 235.

Origin of fissile

1655–65; < Latin fissilis, equivalent to fiss(us) (see fissi-) + -ilis -ile
Related formsfis·sil·i·ty, nounnon·fis·sile, adjectivenon·fis·sil·i·ty, nounun·fis·sile, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for fissile


  1. British capable of undergoing nuclear fission as a result of the impact of slow neutrons
  2. US and Canadian another word for fissionable
  3. tending to split or capable of being split
Derived Formsfissility (fɪˈsɪlɪtɪ), noun

Word Origin for fissile

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

Word Origin and History for fissile

1660s, from Latin fissilis "that which may be cleft or split," from fissus, past participle of findere (see fissure).

Online Etymology Dictionary, © 2010 Douglas Harper