1.  fusion(n = noun.event) merger, unification - an occurrence that involves the production of a union;
is a kind of union
Derived form verb fuse₁

2.  fusion(n = noun.state) coalition - the state of being combined into one body;
is a kind of unification, union
has particulars: alliance, confederation, federalisation, federalization

3.  fusion(n = noun.process) - the merging of adjacent sounds or syllables or words;
is a kind of linguistic process
has particulars: syncretism

4.  fusion(n = noun.process) nuclear fusion, nuclear fusion reaction - a nuclear reaction in which nuclei combine to form more massive nuclei with the simultaneous release of energy;
is a kind of nuclear reaction
has particulars: cold fusion, thermonuclear reaction

5.  fusion(n = noun.cognition) optical fusion - the combining of images from the two eyes to form a single visual percept;
is a kind of beholding, seeing, visual perception

6.  fusion(n = noun.act) spinal fusion - correction of an unstable part of the spine by joining two or more vertebrae; usually done surgically but sometimes done by traction or immobilization;
is a kind of correction

7.  fusion(n = noun.act) - the act of fusing (or melting) together;
is a kind of combination, combining, compounding
Derived forms verb fuse₁, verb fuse₄

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." [1913 Webster]

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

fusion, n.
1 the act or an instance of fusing or melting.
2 a fused mass.
3 the blending of different things into one.
4 a coalition.
5 Physics = nuclear fusion.

Idiom:
fusion bomb a bomb involving nuclear fusion, esp. a hydrogen bomb.

Derivative:
fusional adj.

Etymology:
F fusion or L fusio (as FUSE(1))

N  combination, mixture, junction, union, unification, synthesis, incorporation, amalgamation, embodiment, coalescence, crasis, fusion, blending, absorption, centralization, alloy, compound, amalgam, composition, tertium quid, resultant, impregnation, combined, impregnated with, ingrained, imbued inoculated.

N  cooperation, coadjuvancy, coadjutancy, coagency, coefficiency, concert, concurrence, complicity, participation, union, additivity, combination, collusion, association, alliance, colleagueship, joint stock, copartnership, cartel, confederation, coalition, fusion, a long pull a strong pull and a pull all together, logrolling, freemasonry, unanimity, esprit de corps, party spirit, clanship, partisanship, concord, synergy, coaction, cooperating, in cooperation, in league, coadjuvant, coadjutant, dyed in the wool, cooperative, additive, participative, coactive, synergetic, synergistic, favorable to, unopposed, as one, shoulder to shoulder, synergistically, cooperatively, due teste valgono piu che una sola.

N  calefaction, increase of temperature, heating, calefaction, tepefaction, torrefaction, melting, fusion, liquefaction, burning, ambustion, combustion, incension, accension, concremation, cremation, scorification, cautery, cauterization, ustulation, calcination, cracking, refining, incineration, cineration, carbonization, cupellation, ignition, inflammation, adustion, flagration, deflagration, conflagration, empyrosis, incendiarism, arson, auto dafe, boiling, coction, ebullition, estuation, elixation, decoction, ebullioscope, geyser, distillation (vaporization), furnace, blanket, flannel, fur, wadding, clothing, still, refinery, fractionating column, fractionating tower, cracking tower, match, incendiary, petroleuse, cauterizer, caustic, lunar caustic, alkali, apozem, moxa, acid, aqua fortis, aqua regia, catheretic, nitric acid, nitrochloro-hydric acid, nitromuriatic acid, radioactivity, gamma rays, alpha particles, beta rays, X-rays, radiation, cosmic radiation, background radiation, radioactive isotopes, tritium, uranium, plutonium, radon, radium, sunstroke, coup de soleil, insolation, pottery, ceramics, crockery, porcelain, china, earthenware, stoneware, pot, mug, terra cotta, brick, clinker, cinder, ash, scoriae, embers, soot, slag, coke, carbon, charcoal, wood alcohol, turpentine, tea tree oil, gasoline, kerosene, naptha, fuel oil (fuel), wax, paraffin, residue, tar, inflammability, combustibility, diathermancy, transcalency, conduction, convection, radiation, radiant heat, heat conductivity, conductivity, thermal expansion, coefficient of expansion, heated, molten, sodden, r_echauff_e, heating, adust, inflammable, combustible, diathermal, diathermanous, burnt, volcanic, radioactive.

cold fusion, fusion bomb, fusion cooking, fusion reactor, heat of fusion, nuclear fusion, nuclear fusion reaction, optical fusion, spinal fusion