adjective
Definition: Someone who is very loyal to a particular idea, group, or cause and does not want to change, even when it may be necessary.
Example: He is a diehard fan of the team, never missing a game regardless of their performance.
noun
Definition: A person who strongly supports a particular cause, belief, or idea, often refusing to change their opinion or behavior.
Example: He is a diehard fan of the team, never missing a game regardless of the weather.