The Collaborative International Dictionary of English v.0.48:

Suffusion \Suf*fu"sion\, n. [L. suffusio: cf. F. suffusion.]
   1. The act or process of suffusing, or state of being
      suffused; an overspreading.
      [1913 Webster]

            To those that have the jaundice, or like suffusion
            of eyes, objects appear of that color. --Ray.
      [1913 Webster]

   2. That with which a thing is suffused.
      [1913 Webster]

   3. (Zool.) A blending of one color into another; the
      spreading of one color over another, as on the feathers of
      birds.
      [1913 Webster]

WordNet (r) 3.0 (2006):

suffusion
    n 1: the process of permeating or infusing something with a
         substance [syn: permeation, pervasion, suffusion]

Moby Thesaurus II by Grady Ward, 1.0:

30 Moby Thesaurus words for "suffusion":
   blush, blushing, coloring, crimsoning, decoction, diffusion, flush,
   flushing, imbuement, impregnation, infiltration, infusion,
   instillation, instillment, interpenetration, mantling, marination,
   overrunning, overspreading, overswarming, penetration, permeation,
   pervasion, pudency, pudicity, reddening, saturation, soaking,
   steeping, transfusion