Fanatical people are usually irrational, and are not good conversationalists.
They were fanatical about the team and never missed a match.
The cult's followers were filled with fanatical devotion.
fanatical
Fanatical They were fanatical followers of the band. Sarah was very fanatical about One Direction, a band. She was crazy fanatical!! Other ways to use it: She was a huge fan. Cody Simpson had millions of fans at his concert.
Extremists can be fanatical in their actions in a chosen cause. The temperance leader Carrie Nation was considered fanatical after she began using a hatchet to damage bars and saloons.
The prefix for obsessive would be obsism, and the prefix for fanatical would be fanatism.
Fanatical:being over zealous about a subject.For example: People can be fanatical about their favorite sport,religion,celebrity or hobby etc...A way to use this word in speaking, may be:My brother is SO fanatical about football,he won't go anywhere when a games on!
Because of her fanatical views, her friends know better than to discuss religion with her.
Filled with excessive and single-minded zeal.
Another word that can be used to replace the word fanatical is the word manic. You could also check a thesaurus for different options, that may fit what you are writing better.
www.thesaurus.com
Fanatical, enthusiastic.