When a male is performing intercourse on a female (missionary) and defecates into his on hand; and then while continuing to thrust at a steady pace he throws the fecal matter onto the female’s stomach with the intention for it to splatter/explode much like a wet snowball. The male may choose whether or not he would like to scream dirty snowball in celebration of his great accomplishment.
When a man or woman takes a ball-shaped bowl movement on their partner's chest then proceeds to ejaculate onto the feces, forming a gooey white coating around it.
Patrick: DUDE! did you hear what Lauren and Kevin did?
Andrew: No, what????
Patrick: Well Kevin took a shit on Lauren's chest then came on it and it was all gooey and white!
Andrew: Oh My God! I'm so jealous! I've always wanted to give someone a dirty snowball.
The act of a male jacking off into one hand while taking a dump in the other, then smacking his hands together, thus mixing the two together. Once together, the male balls the item up, and throws it at a womans face.