The term guru typically refers to someone considered an expert or highly qualified individual in relationship to the topic in question.
One wag says that the difference between an expert and a guru lies in their answers to a question that begins, "How do I...." The expert aswers, "No problem, you just...." The guru answers, "Why do you want to...," followed by, "Don't do that."
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What's that old joke that goes You know what the word expert means, don't you?