[quote=@Halvtand]

Yes, that is the dictionary definition. It does not answer my question at all and only helps very little. It kind of seems like you didn't actually read the question at all, only the title.

[/quote]

Your question was "how does one define a monster in a world where both animals and monsters are natural?" And my answer was that monsters are natural in this world too. But you are allowed to disagree if you'd like. I really wasn't trying to help, only explain why the word monster works for me.