The Collaborative International Dictionary of English v.0.48:

Polyporus \Po*lyp"o*rus\, n.; pl. Polypori. [NL., fr. Gr.
   poly`s many + ? a pore.] (Bot.)
   A genus of fungi having the under surface full of minute
   pores; also, any fungus of this genus.
   [1913 Webster]

   Note: Polyporus fomentarius was formerly dried and cut in
         slices for tinder, called amadou. Polyporus betulinus
         is common in America, and forms very large thick white
         semicircular excrescences on birch trees. Several
         species of Polyporous are considered edible.
         [1913 Webster]

WordNet (r) 3.0 (2006):

Polyporus
    n 1: type genus of the Polyporaceae; includes important
         pathogens of e.g. birches and conifers [syn: Polyporus,
         genus Polyporus]