According to the U.S. National Library of Medicine's MedlinePlus site, an enlarged stomach is referred to as a "distended abdomen," "swollen belly" or "swelling in the abdomen." The most common cause of a distended abdomen is overeating.
U.S. News and World Report indicates that there are several other common reasons for an enlarged stomach. For example, certain people who have difficulty digesting carbohydrates suffer from a bloated middle. Constipation and acid reflux also contribute to a swollen belly. Digestive issues such as Celiac disease or difficulty digesting wheat or gluten lead to an enlarged stomach. MedlinePlus lists several medical conditions, including lactose intolerance, ovarian cysts, bowel blockage and uterine fibroids, that have a distended abdomen as a symptom.