Etymology: Middle Class American Descriptive Expletive, from Anglo-French "boules aux murs",
1: usually something extremely unbelieveable: something that has elevated something ordinary to new levels of incredulity.
2: something ridiculously defining and causing one to pay closer attention, as though ones testicles have just been body slammed hard into a solid surface such as a wall, or pavenment, or something equally dense and painful in the slamming.
"That was a frigging ballstowalls awesome band, when are they going on tour?"
"Baby when we get down and dirty you get me so ballstowalls horny I can't control myself"
"That was without question the ballstowalls worst proctology exam I have ever experienced dude."