1. having the qualities or appearance of youth; young or seeming young
2. characteristic of young people; energetic and enthusiastic

Examples

• Despite being sixty, she maintained a youthful appearance.
• His youthful enthusiasm impressed the entire team.
• The actress looked remarkably youthful in the new film.
• She approached the challenge with youthful energy.
• The old building was given a youthful makeover.
• His youthful optimism was contagious.
• The grandmother had a youthful spirit that inspired everyone.