Snowballing or snowdropping is the human sexual practice in which one person takes someone else's semen into his or her mouth and then passes it to the mouth of the other, usually through kissing.
The term was originally used only by homosexuals. Researchers who surveyed over 1,200 gay or bisexual men at New York LGBT community events in 2004 found that around 20% said they had engaged in snowballing at least once. In heterosexual couples, a woman who has performed fellatio may afterwards return the semen to her partner's mouth, mixed with saliva; the couple or other partners may then exchange the fluid several times, causing its volume to increase (hence "snowballing"). Many heterosexual men are uncomfortable with the practice.