An Etymological Dictionary of Astronomy and Astrophysics

1. The act or process of fusing; the state of being → fused; that which is fused; the result of fusing.
   

2. A → nuclear reaction between atomic nuclei (→ nucleus) as a result of which a heavier nucleus is formed and a large quantity of → nuclear energy is released. → proton-proton chain, → CNO cycle, → nucleosynthesis.
   

3. Change of the → state of a → substance from → solid to → liquid which occurs at a definite → temperature at a given applied → pressure. Same as melting.

Etymology (EN): From M.Fr. fusion, from L. fusionem, from fusus, p.p. of fundere “to pour, melt.”

Etymology (PE): Verbal noun form of → fuse.