tribadism is a common non-penetrative sexual act between women. it is often known by its "scissoring" position, and is also referred to as frottage or in popular slang as dry humping. it involves a woman rubbing her vulva against her partner's vulva, thigh, stomach, buttocks, arm, or another body part. this may be achieved in a number of sex positions, including a missionary, a woman on top, doggy style, scissoring or other position. it may be accompanied by fingering or penetration with a dildo.