1. The act or procedure of liquefying or melting by the application of heat.
2. The merging of different elements into a union; such as, the fusion of copper and zinc to form brass.
3. A union resulting from fusing; for example, a fusion of religion and politics emerged when the leaders got together to iron out their differences.
4. Correction of an unstable part of the spine by joining two or more vertebrae; usually done surgically but sometimes done by traction or immobilization.
5. The merger or a blending of two or more things; such as, materials or ideas.
6. The process of melting or the conversion of a solid into a liquid by means of heat or pressure.
7. A nuclear process in which two light nuclei combine at extremely high temperatures to form a heavier nucleus and release vast amounts of energy.

The energy of the sun and other stars is believed to derive from fusion reactions.

1. A process in which strong electron beams implode tiny pellets of deuterium and tritium, causing them to attain the temperature and density needed to initiate a fusion reaction.
2. The use of intense beams of electrons to implode small pellets of deuterium and tritium so that they reach the temperature and density required for initiating a fusion reaction.

A nuclear reactor that produces energy by fusing light nuclei together, instead of splitting heavy nuclei apart as in the fission process.

In nuclear energy, a method of internal confinement fusion in which an energy beam of electrons or other particles is directed onto a tiny pellet of a deuterium-tritium mixture, causing it to explode like a miniature hydrogen bomb, fusing the deuterium and tritium nuclei within a time span too short for them to repel each other.