When a scene (film/tv show etc) starts with someone telling the punchline of a joke, without the setup. Usually followed by loud, overly-dramatic laughter from those present.
(Name taken from Tv Tropes).
“So he says “do you love me?” and she says “no, but that's a real nice ski mask!” - Dumb and Dumber.
Orphaned punchline
When a comedian tells a joke or a story, they say the actual funny part at the end and the comedians voice trails off and acts like it’s nothing making it even funnier due to a complete dependence on the audience paying attention, usually ended with a dead stare.
Reverse punchline
I had a nightmare
It was a nightmare about standing in front of a group of people
I said I had nightmares
And they said, nightmares, what are those?
Tim: I’m planing a mass punchline
Jenna: you know that highly illegal