The Collaborative International Dictionary of English v.0.48:

Fusion \Fu"sion\, n. [L. fusio, fr. fundere, fusum to pour,
   melt: cf. F. fusion. See Fuse, v. t., aud cf, Foison.]
   1. The act or operation of melting or rendering fluid by
      heat; the act of melting together; as, the fusion of
      metals.
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   2. The state of being melted or dissolved by heat; a state of
      fluidity or flowing in consequence of heat; as, metals in
      fusion.
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   3. The union or blending together of things, as, melted
      together.
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            The universal fusion of races, languages, and
            customs . . .
            had produced a corresponding fusion of creeds. --C.
                                                  Kingsley.
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   Watery fusion (Chem.) the melting of certain crystals by
      heat in their own water of crystallization.
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   4. (Biol.) The union, or binding together, of adjacent parts
      or tissues.
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