fu·sion (fyo͞oˈzhən)

1. The act or procedure of liquefying or melting by the application of heat.
2. The merging of different elements into a union, as of vertebrae.
3. The mechanism by which both eyes blend slightly different images from each eye into a single image.
4. The growing together of two or more teeth as a result of the abnormal union of their formative organs.
5. A nuclear reaction in which nuclei combine to form more massive nuclei with the simultaneous release of energy.