What does moi o si mean?

"Moi o si" doesn't appear to be a recognized phrase in any common language. It's possible that:

* There's a typo: Could you double-check the spelling?

* It's a specific term: Is this from a particular context (like a book, movie, or game)? Knowing the source might help figure out the meaning.

* It's a made-up phrase: Perhaps it's a fictional language or a playful invention.

Please provide more information about the context where you encountered this phrase, and I can help you figure out what it means.