a B.I.D will act all friendly and pretend they are sweet and kind to everyone, but as soon as you piss one off, they show there true colours.
this can also be them being two faced.
your friends with someone, and they say vindictive things about you to your other friend.
Some guy saying that my little pony is for little girls, but secretly loves it.
Person 2: Yeah man, I hate it.
After both guys get home, they quickly get behind their computer to watch my little pony friendship is magic.
In this scenario, both guys are B.I.D's.