vajrayana karmamudra

Karmamudrā (Sanskrit; "action seal," erroneously: kāmamudrā or "desire seal," Tib. las-kyi phyag-rgya) is tantric yoga involving sexual union with a physical partner, or a visualized simulacrum thereof. The aim of the practice is to control one's sexual energy, and the most advanced forms of yab-yum practice are often done mentally, without using a physical partner. Like all other yogas, it cannot be practiced without the basis of the inner heat yoga, tummo, of which karmamudrā is an extension. This sadhana is subsumed within the Six Yogas of Naropa. The iconography of yab-yum and the maitrī practice of Karmamudrā engenders cognition[1] of the upaya doctrine of interpenetration.

- http://en.wikipedia.org/wiki/Karmamudra