The Collaborative International Dictionary of English v.0.48:

Water brash \Wa"ter brash`\ (Med.)
   See under Brash.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Brash \Brash\, n. [See Brash brittle.]
   1. A rash or eruption; a sudden or transient fit of sickness.
      [1913 Webster]

   2. Refuse boughs of trees; also, the clippings of hedges.
      [Prov. Eng.] --Wright.
      [1913 Webster]

   3. (Geol.) Broken and angular fragments of rocks underlying
      alluvial deposits. --Lyell.
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   4. Broken fragments of ice. --Kane.
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   Water brash (Med.), an affection characterized by a
      spasmodic pain or hot sensation in the stomach with a
      rising of watery liquid into the mouth; pyrosis.

   Weaning brash (Med.), a severe form of diarrhea which
      sometimes attacks children just weaned.
      [1913 Webster]