The Collaborative International Dictionary of English v.0.48:

Mossy \Moss"y\, a. [Compar. Mossier; superl. Mossiest.]
   1. Overgrown with moss; abounding with or edged with moss;
      as, mossy trees; mossy streams.
      [1913 Webster]

            Old trees are more mossy far than young. --Bacon.
      [1913 Webster]

   2. Resembling moss; as, mossy green.
      [1913 Webster]

WordNet (r) 3.0 (2006):

mossy
    adj 1: overgrown with moss [syn: moss-grown, mossy]
    2: (used pejoratively) out of fashion; old fashioned; "moss-
       grown ideas about family life" [syn: fogyish, moss-grown,
       mossy, stick-in-the-mud(p), stodgy]