hydrogen bomb

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

• noun An explosive weapon of enormous destructive power caused by the fusion of the nuclei of various hydrogen isotopes in the formation of helium nuclei.

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

• noun A thermonuclear bomb which derives its destructive power from the fusion of isotopes of hydrogen (deuterium and tritium).

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

• noun a nuclear weapon that releases atomic energy by union of light (hydrogen) nuclei at high temperatures to form helium