The period of time after a set time at which it is no longer socially acceptable to call someone. Usually around 9-10 o'clock. Only to be violated in periods of extreme urgency. Originally coined by Larry David on, "Curb Your Enthusiasm"
Person 1: Oh shit, I forget to tell my friend that he has to meet me at noon tomorrow.
Person 2: Too late now, it's past the cutoff time.