When a not-funny person tries to tell a joke, and as expected, it isn't funny. Generally Followed by an awkward silence and is also the leading cause of conversations ending abruptly.
guy 1: Man, Kobe Bryant is hurt! I hope he can return!
guy 2: Yeah, he needs to win another ring before he breaks every bone in his body playing basketball or something.
guy 1: Was that supposed to be funny? Nice nightmare-ism.