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.
      1913 webster

   2. a mixture of meal or bran and water fed to animals.
      1913 webster

   3. a mess; trouble. obs. --beau.  fl.
      1913 webster

   mash tun, a large tub used in making mash and wort.
      1913 webster
see also:
mix mash tun 

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
see also:
mashed mashing mash mashing tub mash tun mash vat