1. the process of becoming hard or harder; the state of having become hard
2. a process of making someone or something less sensitive, sympathetic, or emotional

1. present participle of harden; to make or become hard or harder
2. present participle of harden; to make someone less sympathetic or emotional

Examples

• The hardening of the concrete took several days.
• Years of difficult experiences led to a hardening of her heart.
• The metal is hardening as it cools.
• Repeated rejection can result in the hardening of one's resolve.
• The hardening of arteries is a common health concern in older adults.
• Cold weather causes the hardening of the ground.
• His attitude showed signs of hardening after the argument.
• The hardening process in steel manufacturing requires precise temperature control.