The Collaborative International Dictionary of English v.0.48:

Syncretism \Syn"cre*tism\, n. [Gr. ?, fr. ? to make two parties
   join against a third: cf. F. syncr['e]tisme.]
   1. Attempted union of principles or parties irreconcilably at
      variance with each other.
      [1913 Webster]

            He is plotting a carnal syncretism, and attempting
            the reconcilement of Christ and Belial. --Baxter.
      [1913 Webster]

            Syncretism is opposed to eclecticism in philosophy.
                                                  --Krauth-Fleming.
      [1913 Webster]

   2. (Philol.) The union or fusion into one of two or more
      originally different inflectional forms, as of two cases.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

syncretism
    n 1: the union (or attempted fusion) of different systems of
         thought or belief (especially in religion or philosophy);
         "a syncretism of material and immaterial theories"
    2: the fusion of originally different inflected forms (resulting
       in a reduction in the use of inflections)

Moby Thesaurus II by Grady Ward, 1.0:

102 Moby Thesaurus words for "syncretism":
   Anschluss, addition, admixture, affiliation, agglomeration,
   aggregation, agreement, alliance, alloyage, amalgamation,
   assimilation, association, blend, blending, cabal, cartel,
   casualness, centralization, coalescence, coalition, combination,
   combine, combo, comminglement, commingling, commixture,
   composition, confederacy, confederation, congeries, conglomeration,
   conjugation, conjunction, consolidation, conspiracy,
   crudity of intellect, denominationalism, eclecticism, ecumenism,
   embodiment, encompassment, enosis, federalization, federation,
   fusion, hookup, immixture, imprudence, inclusion, incorporation,
   indiscreetness, indiscretion, indiscriminateness, indiscrimination,
   insensibility, insensitivity, integration, interfusion,
   interlarding, interlardment, interminglement, intermingling,
   intermixture, junction, junta, lack of feeling, lack of refinement,
   league, marriage, meld, melding, merger, mingling, mixing, mixture,
   package, package deal, partisanism, pluralism, promiscuity,
   promiscuousness, schismatism, sectarianism, sectarism,
   solidification, syndication, syneresis, synthesis, tactlessness,
   tie-up, uncriticalness, undiscriminatingness, undiscriminativeness,
   unfastidiousness, unification, union, unmeticulousness,
   unparticularness, unpreciseness, unselectiveness, untactfulness,
   wedding