"Surreptitiously" scratching your balls by pinching your crotch in front of your pants. When you do so inside your pocket, it is known as "Blue Danubing Mezzo-Piano." Named after the waltz composed by Johann Strauss.
While having a conversation with someone, he began Blue Danubing by very obviously pinching his crotch. I swear I'm going to get that guy some jock itch cream as a graduation present.