Noun) This simply stands for best friend forever. A BFF is someone who has been there for you at all times and will listen to what ever you have to say. They will call you just to see how you are, but that's if they're not with you at the moment. Usually, a BFF is someone you've known most of your life and have been through a lot with them.
Thad: Dude, why are you always with Yamila?
Sonny: It's simple, she's my BFF.
Greg: What does BFF stand for?
Sonny: Best Friend Forever, idiot.