The Collaborative International Dictionary of English v.0.48:

Unification \U`ni*fi*ca"tion\, n. [See Unify.]
   The act of unifying, or the state of being unified.
   [1913 Webster]

         Unification with God was the final aim of the
         Neoplatonicians.                         --Fleming.
   [1913 Webster]

WordNet (r) 3.0 (2006):

unification
    n 1: an occurrence that involves the production of a union [syn:
         fusion, merger, unification]
    2: the state of being joined or united or linked; "there is
       strength in union" [syn: union, unification] [ant:
       separation]
    3: the act of making or becoming a single unit; "the union of
       opposing factions"; "he looked forward to the unification of
       his family for the holidays" [syn: union, unification,
       uniting, conjugation, jointure] [ant: disunion]

Moby Thesaurus II by Grady Ward, 1.0:

135 Moby Thesaurus words for "unification":
   Anschluss, addition, affiliation, agglomeration, agglutination,
   aggregation, agreement, alignment, alliance, amalgamation,
   articulation, assimilation, association, blend, blending, bond,
   bracketing, cabal, cahoots, cartel, centralization, clustering,
   coadunation, coalescence, coalition, colleagueship, collegialism,
   collegiality, combination, combine, combo, communication,
   composition, comradeship, concatenation, concourse, concurrence,
   confederacy, confederation, confluence, confraternity, congeries,
   conglomeration, conjugation, conjunction, connection,
   consolidation, conspiracy, convergence, copartnership, copartnery,
   copulation, coupling, ecumenism, embodiment, encompassment, enosis,
   federalization, federation, fellowship, fraternalism, fraternity,
   fraternization, freemasonry, fusion, gathering, hookup,
   identification, identity, inclusion, incorporation, individuality,
   indivisibility, intactness, integrality, integration, integrity,
   intercommunication, intercourse, interlinking, interlocking,
   inviolability, irreducibility, joinder, joining, jointure,
   junction, junta, knotting, league, liaison, linkage, linking,
   marriage, meeting, meld, melding, mergence, merger, merging,
   oneness, organic unity, package, package deal, pairing,
   particularity, partnership, purity, selfsameness, simplicity,
   singleness, singularity, sodality, solidarity, solidification,
   solidity, sorority, splice, symbiosis, syncretism, syndication,
   syneresis, synthesis, tie, tie-in, tie-up, undividedness,
   uniformity, union, uniqueness, unity, univocity, wedding,
   wholeness, yoking



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

unification

    The generalisation of pattern matching that is
   the logic programming equivalent of instantiation in
   logic.  When two terms are to be unified, they are
   compared.  If they are both constants then the result of
   unification is success if they are equal else failure.  If one
   is a variable then it is bound to the other, which may be any
   term (which satisfies an "occurs check"), and the
   unification succeeds.  If both terms are structures then each
   pair of sub-terms is unified recursively and the unification
   succeeds if all the sub-terms unify.

   The result of unification is either failure or success with a
   set of variable bindings, known as a "unifier".  There may
   be many such unifiers for any pair of terms but there will be
   at most one "most general unifier", other unifiers simply
   add extra bindings for sub-terms which are variables in the
   original terms.

   (1995-12-14)