ruggedness

Noun

• the quality of being difficult to do
  • he assigned a series of problems of increasing hardness
    
  • the ruggedness of his exams caused half the class to fail
    

• the quality of being topologically uneven
  • the ruggedness of the mountains
    

• the property of being big and strong

Related words

• Synonyms: 
  hardness , huskiness , toughness