Involuntary swearing and profanity. From the Greek copro- meaning "feces", and -lalia, meaning "babble."
Frequently mischaracterized as the major symptom of Tourette Syndrome in the movies, it is in fact found in less than 10% of Tourette sufferers. And, just as not all Tourette patients exhibit coprolalia, not all coprolalia incidents are a result of Tourette.
Compare to coprographia (drawing inappropriate pictures) and copropraxia (performing inappropriate gestures.)