The Collaborative International Dictionary of English v.0.48:

Silvan \Sil"van\, n. (Old Chem.)
   See Sylvanium. [Obs.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Silvan \Sil"van\, a. [L. silva, less correctly sylva, a wood or
   grove, perh. akin to Gr. "y`lh; cf. L. Silvanus Silvanus the
   god of woods: cf. F. sylvain silvan. Cf. Savage.]
   Of or pertaining to woods; composed of woods or groves;
   woody. [Written also sylvan.]
   [1913 Webster]

         Betwixt two rows of rocks, a silvan scene
         Appears above, and groves forever green. --Dryden.
   [1913 Webster]

WordNet (r) 3.0 (2006):

silvan
    adj 1: relating to or characteristic of wooded regions; "a shady
           sylvan glade" [syn: sylvan, silvan]
    n 1: a spirit that lives in or frequents the woods [syn:
         sylvan, silvan]