1. a legendary animal combining features of animal and human form or having the forms of various animals in combination, as a centaur, griffin, or sphinx.
2. any creature so ugly or monstrous as to frighten people.
3. any animal or human grotesquely deviating from the normal shape, behavior, or character.
4. a person who excites horror by wickedness, cruelty, etc.
5. any animal or thing huge in size.
So in terms of villain for my project I need to think along the lines of an anthropomorphic beast pirate. So I've got that figured out it's just finding out why these pirates are monstrous? Is it because of the MacGuffin that they are like this - such as a curse put upon pirates, much like the curse in Pirates of the Caribbean which they are trying to get rid of?
Much more to think of so I will go ahead with a brainstorming session in order to come up with a few ideas as to what my synopsis is going to be.