Of, relating to, or derived from the fusion of atomic nuclei at high temperatures: thermonuclear reactions.
Of, relating to, or characterized by the use of atomic weapons based on fusion, especially as distinguished from those based on fission: thermonuclear war.
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.