Tribadism ( TRIB-ə-diz-əm) or tribbing, commonly known by its scissoring position, is a lesbian sexual practice involving vulva-to-vulva contact or rubbing the vulva against the partner's thigh, stomach, buttocks, arm, or other body parts (excluding the mouth), especially for stimulation of the clitoris. A variety of sex positions are practiced, including the missionary position.

The term tribadism originally encompassed societal beliefs about women's capability of being penetrative sexual partners. Women accused of having been penetrative during sexual activity were subject to ridicule or punishment. In modern times, the term typically refers to various forms of non-penetrative sex between women.

It is analogous to frot, which is penis-to-penis contact between men.