Source : WordNet®

adder's fern
     n : mat-forming lithophytic or terrestrial fern with creeping
         rootstocks and large pinnatifid fronds found throughout
         North America and Europe and Africa and east Asia [syn: {common
         polypody}, {wall fern}, {golden maidenhair}, {golden
         polypody}, {sweet fern}, {Polypodium vulgare}]