Here are a few options you could use:
* "Pōpō" (pronounced poh-poh): This word means "animal" or "beast" in general. You could use it to refer to a bull, but it wouldn't be very specific.
* "Kāne" (pronounced kah-nay): This word means "male" and could be used to refer to a bull. However, it is very general and could refer to any male animal.
* "Bulu" (pronounced boo-loo): This is the English word "bull" pronounced with a Hawaiian accent. It's not technically a Hawaiian word, but it's commonly understood.
Ultimately, the best way to refer to a bull in Hawaiian would depend on the context. If you're talking about a specific breed of bull, you could use the English word or use a more descriptive phrase.