Jokeblocking

Noun (johk-blok-ing)

Jokeblocking, an act usually carried out by a jokeblocker, is the gesture of deliberately ruining someone's attempt to tell a joke or cause others to laugh, either by distraction or dismissal. Not to be mistaken for cockblocking

Danny: Hey, listen to this joke! "Knock, kno-"
George: Dude that was funny three fucking years ago.
Danny: Damn, stop jokeblocking me.