R.F.F stands for Reverse Feminine Fart
In other words, a queif. Many girls use the word rff insetad of quief because quief sounds gross and it sounds like something that can only happen during sex. Girls that can rff usually put their legs in the air to get the air up their parts and then they can rff on command. Some girls have to get the air and then stand up to rff.
Chandler laid down and put her legs up in the air. She felt the air going in and let out a loud rff. All her friends giggled.
Marina- "Jill! Guess what? I learned how to rff!!"
Jill- " Dude, Marina, I learned how to do that a week ago."