atomic bomb

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An explosive weapon of great destructive power derived from the rapid release of energy in the fission of heavy atomic nuclei, especially of uranium-235 or plutonium-239.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A nuclear weapon that obtains its destructive energy from nuclear fission

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a nuclear weapon in which enormous energy is released by nuclear fission (splitting the nuclei of a heavy element like uranium 235 or plutonium 239)