noun

• (India) Any general teacher (as a term of respect).
• (sometimes humorous) An influential advisor or mentor.
  "Many oenophiles rely on the ratings and recommendations of wine guru Robert Parker when selecting the perfect bottle."
• (derogatory) A fraudster or conman relying on a projected air of confidence in an obscure field.
  "OPCA gurus are modern legal alchemists. They promise gold, but their methods are principally intended to impress the gullible, or those who wish to use this drivel to abuse the court system. Any lack of legal success by the OPCA litigant is, of course, portrayed as a consequence of the customer’s failure to properly understand and apply the guru's special knowledge."