What is "tummo"

n. A Tibetan Buddhist discipline supposed to create heat in the body.

Tummo (Tibetan: gtum-mo; Sanskrit: caṇḍālī) is a form of breathing, found in the Six Yogas of Naropa, Lamdre, Kalachakra and Anuyoga teachings of Tibetan Vajrayana. Tummo originally derives from Indian Vajrayana tradition, including the instruction of the Mahasiddha Krishnacarya and the Hevajra Tantra. The purpose of tummo is to gain control over body processes during the completion stage of 'highest yoga tantra' ( Anuttarayoga Tantra) or Anuyoga.