Snowballing or semen swapping is a human sexual practice in which one person takes into their mouth the semen of another person, and then 'swaps' it back and forth with another person through kissing or spitting.

In a heterosexual context, snowballing is when a man receives his own semen from the mouth of his female partner, into which he has ejaculated. This may appeal to a male who wishes to adopt a passive or submissive role (which conventional fellatio does not entail).

In the more common homosexual context, a man or men may share the taste of one man's semen by kissing or spitting the semen before swallowing.

Snowballing is often featured in pornography, sometimes as part of a practice called bukkake. Here, men generally adopt the dominant role, and semen is passed between women's mouths. Instead of spitting the semen, a much more common practice is that one woman simply opens her mouth and lets the semen flow very slowly or even trickle into the other woman's mouth; this process is slower and so it takes more time on video. Also, a certain minimum distance between mouths is kept to better see the actual fluid that is swapped.

Because snowballing a man's semen involves the exchange of bodily fluids without any barrier, it is not a form of safer sex. Risks are presumably similar to those of unprotected oral sex.

In case you were wondering, by the way: