The Collaborative International Dictionary of English v.0.48:

Cladonia \Cladonia\ n.
   the type genus of Cladoniaceae; lichens characterized by a
   crustose thallus and capitate fruiting bodies borne on simple
   or branched podetia.

   Syn: genus Cladonia.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Cladonia
    n 1: type genus of Cladoniaceae; lichens characterized by a
         crustose thallus and capitate fruiting bodies borne on
         simple or branched podetia [syn: Cladonia, genus
         Cladonia]