Cursing with or at your friends as a joke or to tease them.
Made popular by the movie, Mean Girls.
Friend has a revealing shirt on...
Friend A: Wow, you're such a whore.
Friend B(with low-cut shirt): Thanks, bitch.
Friend C: Oh my god, I can't believe you called Jenny a whore!
Friend A: Geez, chill... It was just a friend curse.
Friend C: ohh hahaa