It's possible that:
* It's a misspelling: Could it be a different word, like "Gustav"?
* It's a proper name: If it's a name, you'd have to know its origin to guess the pronunciation.
* It's a made-up word: In this case, the pronunciation would depend on the person who created the word.
To help me understand and give you a better answer, please:
1. Provide more context: Where did you see this word? Was it in a book, online, or in conversation?
2. Is it a name? If so, what is the origin of the name?
Once I have more information, I can give you a more accurate pronunciation.