* A misspelling of another word: Perhaps it's a typo for "hew," "hue," or "huge."
* A sound effect: It could be a representation of a sound like a "whoosh" or a "whizz."
* A slang term: It might be an informal or regional term, but without context, it's impossible to know.
To get a better understanding of what "Hyuuu" means, please provide more context.
For example:
* Where did you see or hear it? (e.g., online, in a book, in a conversation)
* What was the surrounding text or conversation?
* Was it written or spoken?
With more information, I can help you figure out the meaning.