contraction and release of the urinary passage in the female body to stimulate Swadhisthana chakra and promote brahmacharya ...
practice involving physical contraction of muscles around the urethra and directing the energy upward; a technique for raising energy
Sahasrara Chakra ...
After practising moorcha pranayama, shanmukhi mudra, moola bandha, vajroli/sahajoli mudra and brahmari pranayama first for a few minutes, start the practice of nada yoga in the following manner. Plug both the ears.
But the isolated contraction of the muscles that control the flow of urine is actually vajroli or sahajoli mudra. For full mula bandha, you must also lift the pelvic diaphragm, mostly by contracting the muscles called the levator ani.
cin mudra, sambhavi mudra, khechari mudra, ashwini mudra, maha mudra, mahabeda mudra, yoga mudra, shakti chalana mudra, yoni mudra, Sanmukhi mudra, Naumukhi mudra, Prana mudra, Viparit karana mudra, vajroli mudra, amaroli mudra, sahajoli mudra, ...
also describes Mudras or gestures or Mental attitude, which induce the state of Pratyahar (Sense withdrawal) and results in spontaneous state of meditation. Several mudras are mentioned in the Hatha Yoga which include, Vajroli Mudra, Sahajoli Mudra, ...
See also: Yoga, Body, Pranayama, Meditation, Mind