A sexual act similar to snowballing, in which a male or female recipient accepts a male's semen into his or her mouth and spits it back into the male's mouth. Blowballing involves all the same steps except that the recipient also vomits back into the male's mouth, either by swallowing and purging the semen or holding the semen in their mouth and inducing vomiting. The male them swallows both the recipient's vomit and their own semen.
Sometimes blowballing is a botched attempt at snowballing
Tom was very upset when Mary attempted blowballing him. His shirt was ruined by the attempt.