(noun) Catch-all derogatory expression meaning ridiculous, lame, lucky, or a fluke. Most often used in exasperation by the party who has just been defeated or screwed over by a longshot, lucky bounce, or otherwise flukey play.
Maaaannnn, I can't believe you made that lucky shot. That is just so scrotismal.
(verb): to succeed at doing something by luck or otherwise less than honorable means. A fluke. Most often used in sports. Like if you shank a golf shot, but it somehow goes in the hole anyway. Or if you call swish, but then the basketball miraculously goes off the backboard and through the hoop.
WTF? I can't believe you scrotered that last shot into the basket.
Clint Dempsey totally scrotered that ball past Robert Green in the World Cup.
A surfer who lacks the appropriate balance required for proficiency, thus needing his feet to be planted wider than normal in order to not fall off the board. Usually a beginner or otherwise kook lacking style.
Look at that wide stance kook proning in the whitewater!