Coined from the hit movie "Mean Girls" by the
excellent actress
Rachel McAdams. It can mean many things, either friendly or non. Mostly used as a greeting, or as a burn, bitch. It's a flexible saying, but be sure you're friendly before using in a joking manner, it could be
offensive as well.
Jeanean: "Hey Kylie!"
Kylie: "Boo you whore! what are you up to girl?"
+++
Geneva: "I'm so upset! My
boyfriend David broke up with me!"
Olivia: "Boo, you whore-- get over it!"
+++
Barbie Barbara: "Damn, I'm hot in my A&F jeans."
Emo Emily: "Boo,
you fucking whore! Get over yourself,
cake face!"