Tribadism ( TRIB-ə-diz-əm) or tribbing, commonly known by its scissoring position, is a lesbian sexual practice in which a woman rubs her vulva against her partner's body for sexual stimulation, especially for stimulation of the clitoris. This may involve vulva-to-vulva contact or rubbing the vulva against the partner's thigh, stomach, buttocks, arm, or other body part (excluding the mouth). 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 may also involve vaginal penetration by use of the fingers, a dildo or double penetration dildo.