Source : WordNet®

rock brake
     n 1: any of several small lithophytic ferns of tropical and warm
          temperate regions [syn: {cliff brake}, {cliff-brake}]
     2: dwarf deciduous lithophytic ferns
     3: chiefly lithophytic or epiphytic fern of North America and
        east Asia [syn: {rock polypody}, {American wall fern}, {Polypodium
        virgianum}]