Wiktionary
n. (context psychotherapy English) The use of breathing as therapy, particularly changing the breathing rhythms.
Wikipedia
Breathwork is an umbrella term for various New Age practices in which the conscious control of breathing is meant to influence mental, emotional and physical state – sometimes to claimed therapeutic effect.
Breathwork can cause distress and has no proven positive health impact other than perhaps promoting relaxation.
There are many types of Breathwork which have emerged over the last few decades, including Integrative Breathwork, Transformational Breathwork, Shamanic Breathwork, Conscious Connected Breathing, Radiance Breathwork, Zen Yoga Breathwork and many others.
Older non-Western techniques such as Yoga, Pranayama, T'ai chi, and Qigong are also offered as systems where the breath is used to direct and enhance the body's energy and aid in the release of old emotions. Similarly the many schools and teachers of mindfulness are also using breathing techniques that can date back to and beyond the time of the Buddha.
Usage examples of "breathwork".
As Reynolds (1994) summarizes the Grofian view: "The clinical data Grof has collected during therapy sessions of LSD and holotropic breathwork indicates a very fluid accessibility to all the domains of consciousness.
But those already evolved structures (phylogenetic and ontogenetic) can indeed be recovered by any techniques that sufficiently lift the repression/amnesia barrier (LSD, yoga, breathwork, intense stress, etc.
My respect and admiration for Grof's work is well known, and I am a major fan of his holotropic breathwork (I think it is a significant contribution to the technologies of experiential disclosure).