The Collaborative International Dictionary of English v.0.48:

Interfusion \In`ter*fu"sion\, n. [L. interfusio.]
   The act of interfusing, or the state of being interfused.
   --Coleridge.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

30 Moby Thesaurus words for "interfusion":
   admixture, alloy, alloyage, amalgam, amalgamation, blend, blending,
   coalescence, combination, comminglement, commingling, commixture,
   composition, eclecticism, fusion, immixture, integration,
   interlarding, interlardment, interminglement, intermingling,
   intermixture, interpenetration, interspersion, merger, mingling,
   mixing, mixture, pluralism, syncretism