The term UNRETURED SERVES is a job description for an ACE, which stands for 'Athletic Club Employee'. An ACE is responsible for providing customer service to members of a sports club or gym. They are also responsible for ensuring that all equipment is in working order and that the facility is kept clean and safe. Additionally, they must ensure that all members adhere to the rules and regulations of the facility. An ACE must also be able to handle any unreturned serves that may occur during a game or match.