The Collaborative International Dictionary of English v.0.48:

Interfuse \In`ter*fuse"\, v. t. [L. interfusus, p. p. of
   interfundere to pour between; inter between + fundere to
   pour. See Fuse to melt.]
   [1913 Webster]
   1. To pour or spread between or among; to diffuse; to
      scatter.
      [1913 Webster]

            The ambient air, wide interfused,
            Embracing round this florid earth.    --Milton.
      [1913 Webster]

   2. To spread through; to permeate; to pervade. [R.]
      [1913 Webster]

            Keats, in whom the moral seems to have so perfectly
            interfused the physical man, that you might almost
            say he could feel sorrow with his hands. --Lowell.
      [1913 Webster]

   3. To mix up together; to associate. --H. Spencer.
      [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

53 Moby Thesaurus words for "interfuse":
   add, amalgamate, assimilate, blend, coalesce, combine,
   come together, compound, comprise, connect, consolidate, diffuse,
   embody, encompass, flux, fuse, immingle, impregnate, include,
   incorporate, infuse, integrate, interblend, interlard, intermingle,
   intermix, interpenetrate, intersow, intersperse, intersprinkle,
   join, lump together, make one, meld, melt into one, merge, mingle,
   mix, penetrate, percolate, pervade, put together, reembody,
   roll into one, saturate, shade into, solidify, syncretize,
   syndicate, synthesize, transfuse, unify, unite