There need to be perfect conditions for the thermonuclear reaction to take place.
1938 with reference to stars, 1953 of weapons (technically only to describe the hydrogen bomb), from thermo- + nuclear.
Relating to the fusion of atomic nuclei at high temperatures or to the energy produced in this way.
Relating to weapons based on nuclear fusion, especially as distinguished from those based on nuclear fission.
A term referring to devices that use nuclear fusion, the fusion of atomic nuclei, to produce energy at very high temperatures. (See hydrogen bomb.)