The Collaborative International Dictionary of English v.0.48:

Lambskin \Lamb"skin`\, n.
   1. The skin of a lamb; especially, a skin dressed with the
      wool on, and used as a mat. Also used adjectively.
      [1913 Webster]

   2. A kind of woolen.
      [1913 Webster]

WordNet (r) 3.0 (2006):

lambskin
    n 1: the skin of a lamb with the wool still on
    2: skin of a sheep or goat prepared for writing on [syn:
       parchment, sheepskin, lambskin]