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