Filling a smoking deceive of your choice (i.e. pipe, bong) with marijuana. Or in other terms "Packing a Bowl". The words "packing a bowl" is shortened to the letters P and B. but when typing on facebook or writing a note to someone, the proper spelling would be "Pee a Bee"
"Hey dude im bored, lets pee a bee"
"Im so high right now! i just peed like 5 bees"
"Im dry and have no bee to pee..."