Disorder in the large intestine that leads to bloating, diarrhea, constipation, abdominal pain, or mucus in stool.   More…

Merriam-Webster Online Dictionary
irritable bowel syndrome (noun)
a chronic functional disorder of the colon that is characterized especially by constipation or diarrhea, cramping abdominal pain, and the passage of mucus in the stool - abbreviation IBS