The Collaborative International Dictionary of English v.0.48:

Plash \Plash\, v. i. [imp. & p. p. Plashed; p. pr. & vb. n.
   Plashing.] [Cf. D. plassen, G. platschen. Cf. Splash.]
   To dabble in water; to splash. "Plashing among bedded
   pebbles." --Keats.
   [1913 Webster]

         Far below him plashed the waters.        --Longfellow.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Plash \Plash\, v. t. [imp. & p. p. Plashed; p. pr. & vb. n.
   Plashing.] [OF. plaissier, plessier, to bend. Cf.
   Pleach.]
   To cut partly, or to bend and intertwine the branches of; as,
   to plash a hedge. --Evelyn.
   [1913 Webster]