Sanskrit प्राणायाम for “restraint (ayama) of energy, life force (prana).” A type of breathing exercise which transforms the life force (sexual energy) of the practitioner. There are many types of pranayama taught in the Gnostic tradition. You can learn some of them in the books The Major Mysteries, Kundalini Yoga, and The Yellow Book.
"Pranayama is a system of sexual transmutation for single persons." - Samael Aun Weor, The Yellow Book
"Many Asanas and exercises of Pranayama exist, but the former exercise of Pranayama [given in this book] is enough for the transmutation of the student’s sexual energies. [...] Oriental Yoga gives a great variety of exercises for Pranayama. Let us see: deep breathing exercise, Sukha Purvaka (easy, comfortable) Pranayama during walking, Pranayama during meditation, Rhythmical breathing, Suryabheda, Ujjayi, Sitkari, Sitali, Bhastrika, Bhramari, Murchha, Plavini, Kevala Kumbhaka, etc. All of these innumerable varieties of practices and Asanas (postures) served for the descending arch of the evolving life; yet, now we are starting an ascending arch of evolution, and therefore, that enormous quantity of postures and exercises are antiquated for the new Aquarian era." - Samael Aun Weor, Kundalini Yoga