1. sells more of something than is available or can be delivered
2. promotes or advertises something in an exaggerated or misleading way

Examples

• The airline oversells flights regularly, knowing some passengers will not show up.
• The marketing team oversells the product's capabilities in their advertisements.
• He oversells his experience on his resume, claiming skills he doesn't actually have.
• The company oversells tickets to the concert and must compensate angry customers.
• She tends to oversell her ideas in meetings, making them sound better than they really are.
• The retailer oversells inventory and cannot fulfill all orders on time.