a spell used at hogwart's causing one's opponent to begin shitting uncontrolably, often with violence. Usually results in dehydration.
voldemorte was taken by surprise when Harry Potter shouted RECTUS EXPELLARUM!!!, As a result, the death eaters were covered in shite like an audience at a Galagher performance.
by cassius$ July 19, 2006
Get the rectus expellarummug.