This is a naturally occurring phenomenon that happens during intercourse. When a man is giving his finest sexual efforts and climaxes inside of his woman but with the women on top. You are then left in the situation where the seminal fluid is held inside the vagina with nothing but a penis stopping its gravitational exit onto your belly.
The moment at which the female "gets up offa that thing", the genitally enforced seal is released and the contents emptied all over your lower abdomen ... rather like the upturning of a freshly opened yogurt pot.
This is when you cum inside your own, or someone else's belly button, then stick a lid (such as sello-tape or cling film) to hold the substance in place.