kapalabhati

A fairly aggressive form of pränayama involving forcibly expelling air from the lungs as the diaphragm and abdominal muscles contract.

Kapalabhati pranayama.
An active yogic breathing practice, also known as “skull shining breath,” which consists of a rapid succession of forceful exhalations and passive inhalations. This practice is cleansing, invigorating, and balancing to vata, pitta, and kapha; it purifies the pranic channels (srotamsi) without creating heat.

Source: http://www.banyanbotanicals.com/info/ayurvedic-living/learning-ayurveda/glossary-of-ayurvedic-terms/