Definition - What does Ru mean?
Ru is a Sanskrit word that translates as “sound,” “noise,” “alarm,” “howling,” “crying,” “injuring,” “fear,” “to break” or “shatter.” It also forms the root of ruc, a Sanskrit word meaning “light” or “splendor,” which may be the source of a common translation of “guru” in the yoga world.
Guru means “teacher,” although it suggests a deeper relationship than the Western world's idea of an instructor. A guru is a spiritual master who guides a yogi on his journey to enlightenment.
Yogapedia explains Ru
Guru is often translated as “one who dispels darkness.” Many sources break the word down into the root gu, which they translate as “darkness,” and the root ru, which they translate as either “remover,” “dispeller” or “light.” Sanskrit dictionaries translate gu as “to go,” “earth” and even “water,” so the darkness may refer to the ignorance of the material world.
Regardless of its accuracy, the translation of gu and ru by the yoga world has spiritual significance that emphasizes the importance of the guru in dispelling ignorance (darkness) and providing the light of wisdom and true knowledge.