I noticed that the acronym BFF Stands for Best Friend Forever over on The Urban Dictionary. I'd always assumed it meant Best Female Friend, meaning the close-but-platonic woman-friend of a straight bloke who also has his bloke mates. He can also confide in this BFF and get female advice from her. So presumably when I've said BFF before, people have not really understood me... until perhaps now. The Urban Dictionary have published this- my third entry. Check definition 19.
BMF (Best Male Friend) is already in the UD under definition 13.