a guru is simply a teacher. Someone who is an expert at something. Someone who teaches

Guru (Devanagari ????) is a Sanskrit term for “teacher” or “master”, particularly in Indian religions. The Hindu guru-shishya tradition is the oral tradition or religious doctrine or experiential wisdom transmitted from teacher to student. In the United States, the word guru is a newer term, most often used to describe a teacher from the Hindu tradition. In the West some derogatory interpretations of the word have been noted, reflecting certain gurus who have allegedly exploited their followers’ naiveté, due to the use of the term in certain new religious movements

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