diehard (also die-hard)
noun

- someone who is unwilling to change or give up their ideas or ways of behaving, even when there are good reasons to do so

(Cambridge Advanced Learner's Dictionary)

adjective

- stubbornly resisting change or clinging to a seemingly hopeless or outdated cause

(American Heritage Dictionary)

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Although most dictionaries define a diehard in a negative context of someone who is opposed to change, the term is also used in a positive sense to describe a person who is passionate about something.

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BLACK HUMOUR

Many sports fan are known as diehards, like the man who had two tickets to see his team play in the football World Cup.

He was sitting by himself next to an empty seat when another fan approached and asked if the seat was taken.

"No," he said. So the other fan sat down and struck up a conversation.

"Can you imagine having a seat right next to the pitch for a World Cup game and not coming?"

"Oh, that was my wife's seat."

"Where is she?"

"She passed away."

"I'm sorry to hear that. No one else wanted to come with you? A brother or a friend?"

"No, they're all at her funeral."

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SYNONYMS

dyed-in-the-wool, extremist, fanatic, old fogy, mossback, old liner, praetorian, stick-in-the-mud, true blue, zealot

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Practice OWAD in a conversation:

"Coffee may be unhealthy, but a DIEHARD like me can't get through the day without having several cups."

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Thanks to Michael for suggesting today's word!