Encopresis

n. unintentional excretion of feces

Encopresis, from the Greek κοπρος (kopros, dung) is involuntary "fecal soiling" in children who have usually already been toilet trained. Children with encopresis often leak stool into their underwear.
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Encopresis is repeatedly having bowel movements in places other than the toilet after the age when bowel control can normally [more]Encopresis - Community and Resources

Noun
1. involuntary defecation not attributable to physical defects or illness
(hypernym) mental disorder, mental disturbance, disturbance, psychological disorder, folie

Inability to control the elimination of stool (fecal incontinence).