Source : Webster's Revised Unabridged Dictionary (1913)

Filtration \Fil*tra"tion\, n. [Cf. F. filtration.]
   The act or process of filtering; the mechanical separation of
   a liquid from the undissolved particles floating in it.

Source : WordNet®

filtration
     n 1: the process whereby fluids pass through a filter or a
          filtering medium
     2: the act of changing a fluid by passing it through a filter