Irritable_bowel_syndrome Irritable bowel syndrome (IBS) is a blanket term for a variety of diseases causing discomfort in the gastro-intestinal tract. It is also called spastic colon, is a functional bowel disorder characterized by chronic abdominal pain, discomfort, bloating, and alteration of bowel habits in the absence of any organic cause. In some cases, the symptoms are relieved by bowel movements.