fusion bomb

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

• noun A nuclear bomb, especially a hydrogen bomb, that derives its released energy principally from fusion reactions among light nuclei.

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

• noun An atomic bomb that uses nuclear fusion as a source of energy; a hydrogen bomb

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