The rate at which one gives gives fewer fucks.
DMFG: G(F)={(D/S)*D{Nbar^2} -- the number of given fucks is equal to the days left in the semester times the distance from you to the nearest bar (Cornell notation replaces Nbar with NBrB)
There's an economic principle at play here. One that I think a lot of people take away from econ courses. It's called the Law of Diminishing Marginal Fucks Given (or DMFG).
The opposite of a performance enhancing drug, like marijuana.
That guy smoked pot before the race and raced like a turtle. It was a performance diminishing drug somebody on the other team told him would make him faster.
A drug that does the opposite of enhance performance, such as marijuana.
Someone from the other team told the guy that if he smoked ganja before the race, he would be more clearheaded, faster, stronger, and to his suprise, it took him most of the day to finish. Nobody told him that marijuana was a performance diminishing drug.