What's your defintion of pretty in a woman?

Just wondering because I see so many questions of girls who do those rate me things or even the one a few minutes ago with a pretty indian woman and people are harsh. Like "she's mediocre" Really? How must a person look to be pretty; seems impossible. I just don't get how the prettiest of woman can be called mediocre. Like Scarlet Johannson. People say she's mediocre, at least at my school, I was just like wow I think she beautiful. Just wondering...