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

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. Some men may do this as a gesture of tenderness and communication after having played the dominant role in power exchange play .

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

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 out the semen, a much more common practice is that one woman reclines, opens her mouth, the other woman leans over her and lets the semen flow very slowly or trickle into the first woman's mouth; this process is slower and so it takes more time on video. Also, a clear distance is kept between their mouths in order to better see the actual fluid that is swapped. In some cases, the semen will then be swallowed by one or both of the actresses.

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 similar to those of unprotected oral sex.

Use of the term in popular culture

The term was popularized by Kevin Smith's film, Clerks, in which the character of Willam Black is nicknamed "Snowball" because he enjoys the practice.

It was additionally noted in the film Stepmom, when Julia Roberts is talking to her stepdaughter about bullying. The term was then misrepresented (called "snow blowing") by the mother whilst having a talk with her children's stepmother. The term is also generally referred to as a cum swap within pornographic films.