The Collaborative International Dictionary of English v.0.48:

Mash \Mash\, n. [Akin to G. meisch, maisch, meische, maische,
   mash, wash, and prob. to AS. miscian to mix. See Mix.]
   [1913 Webster]
   1. A mass of mixed ingredients reduced to a soft pulpy state
      by beating or pressure; a mass of anything in a soft pulpy
      state. Specifically (Brewing), ground or bruised malt, or
      meal of rye, wheat, corn, or other grain (or a mixture of
      malt and meal) steeped and stirred in hot water for making
      the wort.
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   2. A mixture of meal or bran and water fed to animals.
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   3. A mess; trouble. [Obs.] --Beau. & Fl.
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   Mash tun, a large tub used in making mash and wort.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Mash \Mash\, v. t. [imp. & p. p. Mashed; p. pr. & vb. n.
   Mashing.] [Akin to G. meischen, maischen, to mash, mix, and
   prob. to mischen, E. mix. See 2d Mash.]
   To convert into a mash; to reduce to a soft pulpy state by
   beating or pressure; to bruise; to crush; as, to mash apples
   in a mill, or potatoes with a pestle. Specifically (Brewing),
   to convert, as malt, or malt and meal, into the mash which
   makes wort.
   [1913 Webster]

   Mashing tub, a tub for making the mash in breweries and
      distilleries; -- called also mash tun, and mash vat.
      [1913 Webster]