1. becomes hard or firm; makes something hard or firm
Usage: third person singular present tense of ‘harden’
2. becomes less sympathetic or more determined; makes someone less sympathetic
Usage: figurative use

Examples

• The concrete hardens within a few hours.
• Cold weather hardens the ground quickly.
• Her expression hardens when she talks about the incident.
• Years of criticism hardens a person’s resolve.
• The clay hardens as it dries in the sun.
• His attitude hardens whenever someone challenges him.
• The metal hardens after being heated and cooled rapidly.