gu·ru

/ˈguru/ noun, pl -rus [count]

1 : a religious teacher and spiritual guide in Hinduism

2 a : a teacher or guide that you trust

He has been a guru to many young writers.

2 b : a person who has a lot of experience in or knowledge about a particular subject

She's a self-proclaimed financial guru.

Fitness gurus call it the hottest new exercise trend of the year.