Source : Webster's Revised Unabridged Dictionary (1913)

Hydropathy \Hy*drop"a*thy\, n. [Hydro-, 1 + Gr. ?, ?, to
   suffer.]
   The water cure; a mode of treating diseases by the copious
   and frequent use of pure water, both internally and
   externally.

Source : WordNet®

hydropathy
     n : the internal and external use of water in the treatment of
         disease [syn: {hydrotherapy}]