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

Definition categories: attribute, body, consistence, consistency, substance

2. 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

Definition categories: attribute, quality

3. devoid of passion or feeling; hardheartedness

Similar word(s): callosity, callousness, insensibility, unfeelingness

Definition categories: attribute, insensitiveness, insensitivity

4. the quality of being difficult to do

- he assigned a series of problems of increasing hardness

Similar word(s): ruggedness

Definition categories: attribute, difficultness, difficulty

5. excessive sternness

Similar word(s): harshness, inclemency, rigor, rigorousness, rigour, severeness, severity, stiffness

Definition categories: attribute, sternness, strictness