* It's a made-up term: Someone may have created this phrase for a specific context, like a friendly competition between friends who are considered "nerdy."
* It's a typo: Perhaps you meant to write something else, like "nerd duel," which could refer to a playful competition between people considered nerds.
* It's a niche slang term: There might be a specific group of people who use this term with a unique meaning.
To better understand what you're asking, could you provide more context?
For example:
* Where did you encounter this term? (In a book, online, in a conversation, etc.)
* What was the context? (Was it related to gaming, movies, books, or something else?)
With more information, I might be able to help you understand what "ner duel" refers to.