A rupture in smooth muscle tissue protruding through a defect or weakened portion of the abdominal wall: An umbilical hernia is one type of abdominal hernia, or an abnormal protrusion of internal abdominal contents into a defect in the umbilical area which is common in a newborn child.

There are various hernias, as an "inguinal hernia", "umbilical hernia", or "spigelian hernia", in which an anatomical part, such as a section of the intestine, protrudes through an opening, tear, or weakness in the abdominal wall musculature which is a system or an arrangement of muscles in a body or a body part.