What is the definition or description of: umbilical hernia?

Hole in the Wall: An umbilical hernia is a hole in the abdominal wall at the belly button through which the inner layer of the abdominal cavity protrudes, creating a sac. If large enough, organs such as the intestine can enter this sac. If the intestine gets stuck within the sac, we call this an incarcerated hernia; if the blood supply of the intestine is compromised, this is a "strangulated" hernia.

Umbilical hernia: This is a hole in the abdominal wall at the belly button, the location of the umbilical cord during fetal development. It usually closes by itself as it fills with scar tissue. Infants with a hernia here usually resolve by age 4-5. Adults may develop a hole here for unknown reasons, and will see a lump under the skin ("outie") where intra-abdominal contents have passed through the hole.

Belly button hernia : An opening in the abdominal muscles (hernia) centered on your belly button ( umbilicus ) that allows fatty tissue or intestine to bulge thru. Can be painful if contracting the muscle squeezes your intestine and dangerous if a lot of intestine is strangled.