Source : Webster's Revised Unabridged Dictionary (1913)

Infiltration \In`fil*tra"tion\, n. [Cf. F. infiltration.]
   1. The act or process of infiltrating, as if water into a
      porous substance, or of a fluid into the cells of an organ
      or part of the body.

   2. The substance which has entered the pores or cavities of a
      body. --Addison.

            Calcareous infiltrations filling the cavities.
                                                  --Kirwan.

   {Fatty infiltration}. (Med.) See under {Fatty}.

   {Infiltration gallery}, a filter gallery.

Source : WordNet®

infiltration
     n 1: a process in which individuals (or small groups) penetrate
          an area (especially the military penetration of enemy
          positions without detection)
     2: the slow passage of a liquid through a filtering medium;
        "the percolation of rainwater through the soil"; "the
        infiltration of seawater through the lava" [syn: {percolation}]