<p><strong>Noun</strong></p><ul><li>the state or quality of being hard: the hardness of ice.</li><li>a relative degree or extent of this quality: wood of a desirable hardness.</li><li>that quality in water that is imparted by the presence of dissolved salts, especially calcium sulfate or bicarbonate.</li><li>unfeelingness or jadedness; callousness.</li><li>harshness or austerity, as of a difficult existence.</li><li>South Midland U.S. ill will; bad feelings: There's a lot of hardness between those two boys.</li><li>Mineralogy. the comparative ability of a substance to scratch or be scratched by another. Compare Mohs scale.</li><li>Metallurgy. the measured resistance of a metal to indentation, abrasion, deformation, or machining.</li></ul>