The Collaborative International Dictionary of English v.0.48:

Moss \Moss\, v. t. [imp. & p. p. Mossed; p. pr. & vb. n.
   Mossing.]
   To cover or overgrow with moss.
   [1913 Webster]

         An oak whose boughs were mossed with age. --Shak.
   [1913 Webster]