generation phase (Sanskrit, utpatti-krama). The first phase of meditational practice (sādhana) associated with the anuttara-yoga-tantras in general and especially with the so-called ‘Father Tantras’ such as the Guhyasamāja Tantra. The generation phase involves the use of creative imagination or visualization as a means of personal transformation through which the practitioners either visualize a divine being before them (front generation) or as themselves (self-generation) in order to alter their perception and experience of the appearance aspect of reality.

A Dictionary of Buddhism, Oxford University Press, 2003, 2004 (which is available in electronic version from answer.com)