1. (

• hardness ,

) the property of being rigid and resistant to pressure; not easily scratched; measured on Mohs scale ;

2. (

• hardness

) a quality of water that contains dissolved mineral salts that prevent soap from lathering; "the costs of reducing hardness depend on the relative amounts of calcium and magnesium compounds that are present" ;

3. (

• unfeelingness ,
• callousness ,
• callosity ,
• hardness ,
• insensibility

) devoid of passion or feeling; hardheartedness ;

4. (

• hardness ,
• ruggedness ,

) 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" ;

5. (

• severity ,
• severeness ,
• harshness ,
• rigor ,
• rigour ,
• rigorousness ,
• rigourousness ,
• inclemency ,
• hardness ,
• stiffness ,

) excessive sternness; "severity of character"; "the harshness of his punishment was inhuman"; "the rigors of boot camp" ;