Source : Webster's Revised Unabridged Dictionary (1913)

Leach \Leach\, n. (Naut.)
   See 3d {Leech}.

Leach \Leach\, n. [Written also {letch}.] [Cf. As. le['a]h lye,
   G. lauge. See {Lye}.]
   1. A quantity of wood ashes, through which water passes, and
      thus imbibes the alkali.

   2. A tub or vat for leaching ashes, bark, etc.

   {Leach tub}, a wooden tub in which ashes are leached.

Leach \Leach\, v. t. [imp. & p. p. {Leached}; p. pr. & vb. n.
   {Leaching}.] [Written also leech and letch.]
   1. To remove the soluble constituents from by subjecting to
      the action of percolating water or other liquid; as, to
      leach ashes or coffee.

   2. To dissolve out; -- often used with out; as, to leach out
      alkali from ashes.

Leach \Leach\, v. i.
   To part with soluble constituents by percolation.

Leach \Leach\, n.
   See {Leech}, a physician. [Obs.]

Source : WordNet®

leach
     n : the process of leaching [syn: {leaching}]
     v 1: cause (a liquid) to leach or percolate
     2: permeate or penetrate gradually; "the fertilizer leached
        into the ground" [syn: {percolate}]
     3: remove substances from by a percolating liquid; "leach the
        soil" [syn: {strip}]