Guru yoga is a traditional practice in Tibetan Buddhism with methods to blend one's mind with the enlightened mind of a master teacher. This may involve visualizing the teacher. It is one of the four traditional ngöndro practices.
Dilgo Khyentse Rinpoche wrote, "The words Guru Yoga mean union with the nature of the guru". This is not a physical union with the teacher, or even trying to emulate a particular teacher, but specifically relates to the inherent wisdom mind of enlightenment found both in the teacher and in the student.