Lovely question, I must say.
So, beauty for me, is a person or a scene or anything that touches my heart. A person is beautiful if their nature is nice, if they have a laugh which can make you smile just by the radiance of it, if they are kind.
(That, doesn't mean that a person who's sad isn't beautiful. Of course they are, I just used easy ways to explain above.)
I would call a lot of people as pretty, cute, gorgeous; depending on how they look like. But Beautiful is not just a word for me, it's a whole emotion I only dedicate to someone I hold dear or care about.
In general terms, everyone is beautiful until I know them. If I met them and got to know they are rude and mean, their persona and looks will automatically reduce in my vision. They won't be lovely for me anymore.