The Collaborative International Dictionary of English v.0.48:

Filtrate \Fil"trate\, v. t. [imp. & p. p. Filtrated; p. pr. &
   vb. n. Filtrating. ] [Cf. LL. filtrare. See Filter.]
   To filter; to defecate; as liquid, by straining or
   percolation. --Arbuthnot.
   [1913 Webster]