“The Sanskrit word Karmamudra is a technical term utilized in Tibetan Buddhism, specifically in Tantra.
The term can be translated as “action seal” or “desire seal.” is a Vajrayana Buddhist technique of sexual practice with a physical or visualized consort. It refers to a secret level of Tantra in which specially prepared initiates – one male, one female – join sexually in order to harness the power of sex for spiritual development.
Through the “activity” of sexual energy, the initiate can “seal” their consciousness in the clear light (bodhichitta). Karmamudra refers both to this type of practice and sometimes to the woman who practices it.
Karmamudra practice is known in all major Tibetan schools, especially in the Kalachakra Tantra. The prerequisites for this teaching include initiation into the tradition, proven comprehension of the Sutrayana and Mahayana teachings, and the ability to restrain the sexual energy. That is, emission of the sexual energy (orgasm) is not allowed.
By relying upon a Karmamudra as the external condition, the yogi on the high levels of the completion stage practices is led to great bliss…
…here one relies upon one of the four types of mudra, such as the lotus like mudra who possesses all characteristics, has been matured by tantric initiation, and has a high degree of spiritual liberation. Such a consort is known as a mudra, or a Wisdom Lady. For this practice one must understand the oral teachings well and have complete control of the two principal vital energies.
One enters into sexual union with the mudra, which gives rise to the special innate bliss. This causes the vital energies to dissolve just as at the time of death, inducing the clear light of mind to arise with great strength.
This is to be performed not only at the time of controlling the life energies, but also at the time of the three higher activities.
However, this practice is extremely secret and it is not appropriate to say more here. There I will not go into greater detail.”
– Excerpted from “Treatise on the Six Yogas of Niguma” by the Second Dalai Lama.