The Collaborative International Dictionary of English v.0.48:

Prose \Prose\, v. t. [imp. & p. p. Prosed; p. pr. & vb. n.
   Prosing.]
   1. To write in prose.
      [1913 Webster]

   2. To write or repeat in a dull, tedious, or prosy way.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Prosing \Pros"ing\, n.
   Writing prose; speaking or writing in a tedious or prosy
   manner. --Sir W. Scott.
   [1913 Webster]