The Guru is that which transmutes the darkness of ignorance, into - like compost that rots, that thick nurturing ground where we learn - into the light of wisdom, enlightenment, the awareness that all is essentially same/total, whatever you like to call it; it is the transforming quality in your heart.
(
ShantiMayi)
"gu" means darkness and ignorance, and "ru" stands for the
destruction, the dissolution thereof.
According to the
dictionary.
The tradition discerns
4 levels of gurus.