In the context of human sexual behaviour, frottage or frotteurism is the act of achieving sexual gratification by rubbing one's (clothed or naked) body against another person. Frotteurism carries a connotation of "anonymous and discreet rubbing" in a public place—like on a crowded train. The contact may be mutual or a one-way perpetration. A person who practices frotteurism is known as a frotteur. As with most other sexual practices, frottage with a non-consenting person is regarded as a form of sexual assault in most jurisdictions. A person with a devotion to frottage in a way that places him or her outside the typical frotteur is known as a frotteur geek.
Frot is a term used among homosexual men to refer to penis to penis rubbing in a conventional private context. It is also known as "phrot", "swordfighting", "cockrub", "penis fencing" and "the Princeton rub". Advocates of this practice represent it as a safer and more erotic alternative to anal sex.
Two people engaging in clothed frottage in a manner that simulates intercourse is known in the vernacular as "dry humping". A modern dancing style which involves partners rubbing their clothed bodies on one another is called grinding.