1. the process of becoming dark or darker
2. something that makes dark or darker

1. present participle of darken; becoming or making dark or darker

Examples

• The darkening sky warned of an approaching storm.
• She noticed a darkening of his mood after the phone call.
• The darkening clouds blocked out the sun.
• His face showed a gradual darkening as he read the letter.
• The room was darkening as evening approached.
• The darkening of the photograph made it hard to see details.
• We hurried home as the sky was darkening rapidly.