Fanatically means being extremely enthusiastic or dedicated to something.
When people talk about someone fanatically supporting their favorite sports team, they usually mean that this person gets overly excited and is completely obsessed with their team's success. They might wear ridiculous amounts of merchandise, go to every single game, and spend hours discussing the latest scores and player stats. It's like their team is a part of them. Being fanatical can be about anything - music, politics, or even food.
in a passionately fanatic manner
Example: he followed the teachings of his guru fanatically
