A toilet seat that is too round and you end up mashing your wang up against the front of it.
My old apartment's toilet was a total wangmasher.
n An unpleasant and excessively small toilet or toilet seat obviously created by a child, a woman, a midget or a dwarf (or worse a combination thereof) such that it squashes an average man's junk up against the front of the bowl or squeezes his junk up against the seat resulting in sometimes fleeting, sometimes lasting, sometimes permanent discomfort and/or damage to one's johnson.
adj. "wangmashing" - the quality of being a wangmasher
1. noun Man, that toilet's such a wangmasher that I pissed all over my leg trying to sharpton.
2. adjective I just tried to sharpton in my new apartment but now my manhood has gone numb because of that wangmashing shitter.