rock brake

definition: chiefly lithophytic or epiphytic fern of North America and east Asia
example:
speech part: noun
synonyms: rock polypody
definition: dwarf deciduous lithophytic ferns
example:
speech part: noun
synonyms:
definition: any of several small lithophytic ferns of tropical and warm temperate regions
example:
speech part: noun
synonyms: cliff brake cliff-brake

How rock brake is being used?