Of or relating to the changes in the nucleus of atoms with low atomic weight, such as hydrogen, that require a very high temperature to begin.
Example:
During the 1950s and 1960s American families built thousands of home underground shelters to protect themselves from thermonuclear blasts.
The sun's light comes from a sustained thermonuclear reaction deep within it. On earth, such thermonuclear reactions have been used to develop the hydrogen bomb, a bomb based on a fusion reaction that must be triggered by a fission bomb that uses uranium or plutonium. "Little Boy" and "Fatman," the bombs dropped on Hiroshima and Nagasaki to end World War II, were fission bombs. The thermonuclear era began only in 1952, and has produced bombs hundred of times more powerful.