It can be used on its own, but it is typically used as a response to counteract "No big deal" or nbd.
Also for emphasis: pbfd = "Pretty big fucking deal."
Person B: "Uhh... pbfd."
2. In the Christian religion, the birth of Jesus was apparently a pbd.
"ewww that was gross...."
"I'm gonna take a nap to get rid of this PBD."
Quite possibly one of the most delicious things on the planet. (When made right,) a mouth watering mixture of chocolate, peanut butter, sugar and oats.
WARNING: They ARE addictive!!