Mahamudra (Hatha Yoga)
Mahamudra is a hatha yoga gesture (mudra) whose purpose is to improve control over the sexual potential. The sexual potential, associated with apana, is essential in the process of awakening of the dormant spiritual energy (Kundalini) and attaining of spiritual powers (siddhi).
Read more about Mahamudra (Hatha Yoga): Execution, Effect, Traditional Definition