The Collaborative International Dictionary of English v.0.48:

Iceland moss \Ice"land moss`\ (Bot.)
   A kind of lichen (Cetraria Icelandica) found from the
   Arctic regions to the North Temperate zone. It furnishes a
   nutritious jelly and other forms of food, and is used in
   pulmonary complaints as a demulcent.
   [1913 Webster]