(IBS) A condition that causes upset intestines for a long period of time. It is very unpleasant to the sufferer but tends to be harmless and usually does not lead to more serious complaints. The symptoms vary from person to person and from day to day. In order to be diagnosed with IBS, a person must have at least three of the following symptoms: pain in the lower abdomen; bloating; constipation; diarrhea or alternating diarrhea and constipation; nausea; loss of appetite; tummy rumbling; flatulence; mucous in stools; indigestion; constant tiredness; frequent urination; low back pain; painful intercourse for women.