D defs.my
Entry 4 senses Webster, 1913

Fusion

/fyo͞ozh'-ən/ · Fu·sion · IPA /ˈfjuː.ʒən/
01 n. The act or operation of melting or rendering fluid by heat; the act of melting together; as, the fusion of metals.
  1. 1.
    The act or operation of melting or rendering fluid by heat; the act of melting together; as, the fusion of metals.
  2. 2.
    The state of being melted or dissolved by heat; a state of fluidity or flowing in consequence of heat; as, metals in fusion.
  3. 3.
    The union or blending together of things, as, melted together.
    “The universal fusion of races, languages, and customs . . . had produced a corresponding fusion of creeds.” — C. Kingsley.
  4. 4.
    The union, or binding together, of adjacent parts or tissues.(Biol.)
Phrases & compounds
Watery fusion — the melting of certain crystals by heat in their own water of crystallization.