What is shaken man-tini?

A shaken man-tini is a sexual act, named after the alcoholic drink, the martini. It involves emptying the contents of a ballpoint pin and inserting opposite ends into the urethras of two penises until the glans (or heads) of the penises are touching, at which point the males begin to alternate ejaculations, forcing an ever-growing mass of semen back and forth between the penises.