Speedo bathing suit.

When one ejaculates into another ones rectum followed by pull out maneuver which results in a cumshit on the recipients face or hands.

A dude that is constantly touching and fondling his balls and man sack outwardly over the pants or shorts. May be done for pleasure or simply out of boredom. The hallmark of a marble juggler is their juggling act is done in public settings with little regard for creating a spectacle of themselves.

A rock thrown at the general testicular region.

Female clitoral masturbation, cf. jillin.

those wonderful fart noises that sound like bouncing marbles

If you can't figure out what this means, it's probably you.