Short for Peanut Butter Spoon, a snack mainly used by college students and possibly obsessively fit people when you need a snack but poor shopping habits have left you with nothing but condiments and toppings. As such one is then forced to pull out a spoon, scoop up some peanut butter from the jar, and enjoy that spoonful to the fullest.
Roommate 1: What's up?
Roommate 2: PBS time
Roommate 1: Go for it man
Roommate 2: I'm glad I live in a PBS judgement free apartment