Meckel's diverticulum: An outpouching from the small intestine, due to failure of obliteration of the yolk stalk (which normally disappears during embryonic life). About 2% of people have a Meckel's diverticulum. It is usually located about 2 feet (60 cm) above the junction of the small intestine with the colon (the large intestine). A Meckel's diverticulum can become inflamed, ulcerate, bleed, perforate or cause obstruction of the small bowel. If it is inflamed or perforated, it is usually removed by surgery.