The Collaborative International Dictionary of English v.0.48:

Permeation \Per`me*a"tion\, n.
   The act of permeating, passing through, or spreading
   throughout, the pores or interstices of any substance.
   [1913 Webster]

         Here is not a mere involution only, but a spiritual
         permeation and inexistence.              --Bp. Hall.
   [1913 Webster]

WordNet (r) 3.0 (2006):

permeation
    n 1: the process of permeating or infusing something with a
         substance [syn: permeation, pervasion, suffusion]
    2: mutual penetration; diffusion of each through the other [syn:
       interpenetration, permeation]