1. a person or thing that is positioned or falls between two others; something intermediate or transitional
Usage: informal; often used in British English
2. a young person in the age range between childhood and adolescence, or between adolescence and adulthood
Usage: informal; chiefly British
3. in cricket, a batsman who bats in the middle order, between the opening batsmen and the lower order
Usage: sports; chiefly British

Examples

• She felt like an inbetweener, too old for children's activities but not yet ready for adult responsibilities.
• The inbetweener served as a bridge between the two conflicting departments.
• At thirteen, he was an inbetweener, caught between childhood and the teenage years.
• The team's inbetweener batsmen struggled to build a solid middle order.
• That product is an inbetweener in the market—not quite premium, but above budget brands.