thermonuclear

/TH ER0 M OW0 N UW1 K L IY0 ER0/
adjective
  1. 1

    Of, or relating to the fusion of atomic nuclei at high temperatures.

  2. 2

    Of, or relating to the use of atomic weapons based on such fusion, especially as distinguished from those based on fission.

Source: https://en.wiktionary.org/wiki/thermonuclear