to cup someone's balls into your palm and then insert index+middle finger into anus to massage prostate. then pull out fingers covered in shit and wipe onto bottom of nutsack
i gave Pedro R. dirty balls after he tried to rape me, stop giving me dirty balls!, he gave me dirty balls when I kissed his mom
Used in the binge-drinking themed sport of Beer Pong. While the game of beer pong requires that a ping pong ball be thrown from opposite ends of a table into solo drinking cups filled to a level with domestic beer; throwing a "Dirty Ball" is to toss a ping pong ball without rinsing it in the designated "water cup" with the intent of fouling the opponents domestic beer filled cup without their knowledge.
So what, I threw a dirty ball, they were winning by 3 cups and I was wasted!