Tribadism or tribbing is female-to-female genital sex. Two women rub their vulvae together to stimulate each other's clitoris to orgasm, is the act of two women stimulating each other by rubbing their vaginas together in a sort of 'scissor' position, where their vaginas can directly touch each other. It is highly pleasurable and allows for clit-to-clit stimulation, usually resulting in exquisite pleasure for both women.

Tribadism is very pleasurable. It's what some call frottage (from the French verb "to rub" and others call dry humping or dry fucking (though it's not necessarily very dry!) Basically, tribadism is grinding your vulva against some part of your partner's body. You can hump a partner's thigh, rub vulva to pubic bone, or vulva to tailbone. You can do it with clothes on or off. If you have an extremely responsive clit, you may especially appreciate the indirect stimulation.

Tribadism, or tribbing, is female-female genital sex in which the partners rub their vulvas together. Tribadism done with both partners lying on their backs, genitals facing each other, is known as scissors or double Y. It can also be done with one partner on her back and the other in a kneeling position with one leg between the other's legs and the other outside. This usually requires one of the legs of the lying-down partner to be held up, preferably on the shoulder of the kneeling partner. The missionary position is also common.

According to The Oxford English Dictionary, Second Edition, 1989, the word tribadism is formed from the English word tribade, which comes from the French word tribade, which comes from the Latin tribas, a direct transliteration of Greek τριβÜς, from Greek τρßβειν, "to rub."

The earliest usages of the English word tribade cited by OED do not specifically and explicitly refer to either the use of a dildo or direct vulva-to-vulva stimulation. The meaning of the word may have been, at that point, merely "homosexual woman," like the modern meaning of the word lesbian.

It appears that because the English word tribade originally referred to any homosexual woman, tribadism was originally essential a synonym for lesbianism. According to the OED, this is still its primary meaning, although the examples make it clear that from 1965 on, the term is used to describe vulva-to-vulva stimulation specifically.

Colloquially tribbing is known as "bumping fur", "scissoring", "bumping donuts", "clit-clatting", "clam-jousting", "gash mashing", "hamster grappling", "axe grinding", "prawn wrestling", "happy slapping", "biscuit waxing", "horizontal lacrosse", and so on.

Some Central American countries dub the act "making tortillas" since the physical act reminds them of the hand motions used for hand-flattening tortillas, so sometimes lesbians are called "tortilleras" (tortilla makers). And there is the element of the physical resemblance in some minds of the female genitalia to a taco, which is derived from tortillas. In Venezuela, where tortillas are not part of the diet, the analogous slang word is "Cachaperas" (Cachapa makers). Cachapa is a Venezuelan flat-shaped dish made of fresh sweet corn.