Definition of "fissionable" [fis•sion•able]

• Capable of undergoing fission: fissionable nuclear material. (adjective)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "It is only the atoms of mass 235 which are fissionable, that is, from which energy is released."
• "Isotopes of uranium and plutonium which fission in a fast neutron environment are said to be "fissionable", as distinct from fissile."
• "Uranium 238 is not fissile; it is called "fissionable" because it sometimes splits when hit by a fast neutron."