Frottage, also known as ‘frotting’ or just ‘frot’ is a type of ‘outercourse,’ the rubbing of a person’s genintals against another person. The genitals can be rubbed against any body part except the fingers or mouth. When rubbed against fingers or mouth, it becomes something else such as a ‘handjob’ or ‘fellatio.’
The most common version of frottage, and the one for which the term is most often used, is when two men rub their dicks together.
In art, the term ‘frottage’ has an entirely different meaning. It is the act of rubbing charcoal, pastel or other large marking device against a rough paper-covered surface to duplicate the texture visually.
Variations of frot include tribadism in which a vagina is rubbed against another person, and ‘intercrural sex’ in which a penis is placed between upper thighs.
Other names for male-male frotting are the ‘Princeton Rub’ and the ‘Ivy League Rub.’
The act of rubbing two penises together is also commonly known as cock to cock or C2C and usually includes the term jackoff, as in C2C jackoff. Depending upon the talent of the person rubbing both cocks, this can be an extremely enjoyable experience. I’ve done it several times. The most interesting was with a guy who could control his ejaculation to occur exactly when mine did which resulted in two simultaneous spurting cocks. Quite a spectacle.