Definition of "leach"

leach¹

/liːt͡ʃ/

noun
plural leaches
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.
  Quotations
  "This is the leach," said Kitty, pointing to a large, yellowish, upright wooden cylinder, which rested on some slanting boards, down the surface of which ran a brownish liquid that dripped into a trough.
  1894, Robert Barr, chapter 7, in In the Midst of Alarms
3. (nautical) Alternative spelling of leech.
4. A jelly-like sweetmeat popular in the fifteenth century.
  Quotations
  1670, Hannah Woolley, “To make Leach and to colour it”, in The Queen-like Closet, Or, Rich Cabinet

leach²

/liːt͡ʃ/

verb
third-person singular simple present leaches, present participle leaching, simple past and past participle leached
1. (transitive) To purge a soluble matter out of something by the action of a percolating fluid.
  Quotations
  [T]he very wet winter will have washed much of the goodness out of the soil. Homemade compost and the load of manure we get from a friendly farmer may not be enough to compensate for what has leached from the ground.
  2014 April 21, Mary Keen, “You can still teach an old gardener new tricks: Even the hardiest of us gardeners occasionally learn useful new techniques ”, in The Daily Telegraph (Gardening)‎, page G7
2. (intransitive) To part with soluble constituents by percolation.
3. (figurative, intransitive) To bleed, seep.
  Quotations
  A more generic geography, one where the suburb uneasily abuts the commercial and industrial, or leaches out to a nonurban frontier.
  2007, Andrew Shanken, “The Sublime "Jackass"”, in Places, volume 19