The condition in which a person says the letter 's' as a 'sh'. This is not to be confused with a lisp, where the 's' is pronounced as a 'th'. Usually, the holder of this condition also suffers from extreme shortness of attention span. They also seem to be attracted to people who own trucks, usually old pick up trucks with a large back seat.
Speaker 1: That girl just cussed!
Speaker 2: No, she just has a shishp.