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.
      [1913 Webster]

   2. The state of being melted or dissolved by heat; a state of
      fluidity or flowing in consequence of heat; as, metals in
      fusion.
      [1913 Webster]

   3. The union or blending together of things, as, melted
      together.
      [1913 Webster]

            The universal fusion of races, languages, and
            customs . . .
            had produced a corresponding fusion of creeds. --C.
                                                  Kingsley.
      [1913 Webster]

   Watery fusion (Chem.) the melting of certain crystals by
      heat in their own water of crystallization.
      [1913 Webster]

   4. (Biol.) The union, or binding together, of adjacent parts
      or tissues.
      [1913 Webster]

WordNet (r) 3.0 (2006):

fusion
    n 1: an occurrence that involves the production of a union [syn:
         fusion, merger, unification]
    2: the state of being combined into one body [syn: coalition,
       fusion]
    3: the merging of adjacent sounds or syllables or words
    4: a nuclear reaction in which nuclei combine to form more
       massive nuclei with the simultaneous release of energy [syn:
       fusion, nuclear fusion, nuclear fusion reaction]
    5: the combining of images from the two eyes to form a single
       visual percept [syn: fusion, optical fusion]
    6: correction of an unstable part of the spine by joining two or
       more vertebrae; usually done surgically but sometimes done by
       traction or immobilization [syn: fusion, spinal fusion]
    7: the act of fusing (or melting) together

Moby Thesaurus II by Grady Ward, 1.0:

148 Moby Thesaurus words for "fusion":
   Anschluss, addition, admixture, affiliation, agglomeration,
   aggregation, agreement, alignment, alliance, alloy, alloyage,
   amalgam, amalgamation, assimilation, association, blend, blending,
   cabal, cahoots, cartel, centralization, coadunation, coalescence,
   coalition, colleagueship, collegialism, collegiality, colliquation,
   combination, combine, combo, comminglement, commingling,
   commixture, composition, compound, comradeship, confederacy,
   confederation, confraternity, congeries, conglomeration,
   conjugation, conjunction, consolidation, conspiracy, copartnership,
   copartnery, decoagulation, deliquescence, deliquium, dissolution,
   dissolving, eclecticism, ecumenism, embodiment, encompassment,
   enosis, federalization, federation, fellowship, fluidification,
   fluidization, fraternalism, fraternity, fraternization,
   freemasonry, fusibility, fusing, hookup, identification, identity,
   immixture, inclusion, incorporation, individuality, indivisibility,
   intactness, integrality, integration, integrity, interfusion,
   interlarding, interlardment, interminglement, intermingling,
   intermixture, inviolability, irreducibility, junction, junta,
   leaching, league, liquation, liquefaction, liquescence,
   liquescency, lixiviation, marriage, meld, melding, melting, merger,
   mingling, mixing, mixture, oneness, organic unity, package,
   package deal, particularity, partnership, percolation, pluralism,
   purity, running, selfsameness, simplicity, singleness, singularity,
   sodality, solidarity, solidification, solidity, solubilization,
   solution, sorority, syncretism, syndication, syneresis, synthesis,
   thaw, thawing, thermonuclear fusion, thermonuclear reaction,
   thermoplasticity, tie-in, tie-up, unclotting, undividedness,
   unification, uniformity, union, uniqueness, unity, univocity,
   wedding, wholeness



The Free On-line Dictionary of Computing (30 December 2018):

FUSION

   Software package supplied by Network Research Corporation
   claiming to connect various different configurations of LAN.


The Free On-line Dictionary of Computing (30 December 2018):

fusion
vertical loop combination

    A program transformation where a composition
   of two functions is replaced by in-lining them and combining
   their bodies.  E.g.

   	f x = g (h x)	==>	f x = g (2 * x)
   	g x = x + 1		f x = 2 * x + 1
   	h x = 2 * x

   This has the beneficial effect of reducing the number of
   function calls.  It can be especially useful where the
   intermediate result is a large data structure which can be
   eliminated.

   See also vertical loop combination.

   (1994-12-05)