'Best Behaviour Friend'. A friend or
acquaintance in your social
circle, whom you for one reason or another
feel that you should be at your best behaviour around.
"My BBF came to the
party, so I had to restrain myself hugely. If he hadn't been there, I'd have
drunk so much more, and ended up dancing
naked on the tables as I normally do when I've done tequila slammers"