Fecal incontinence refers to the inability to hold feces (stool) in the rectum. This is typically due to failure of voluntary control over the anal sphincters, permitting untimely passage of feces and gas. Fecal incontinence is also known as rectal incontinence or bowel incontinence. Fecal incontinence is not a disease itself but is a symptom that can occur as a result of different kinds of diseases or injuries. Incontinence of stool can result from damage to the nerves or muscles of the rectum and anus, or conditions affecting the intestines. Overflow incontinence, also known as paradoxical diarrhea, occurs in people with chronic constipation when stool fills the rectum, hardens, and becomes impacted. Liquid stool then may leak around the fecal mass, producing symptoms similar to incontinence.

Source: http://www.rxlist.com