落ち (ochi) means “punchline” | MotiTan Japanese Dictionary

More examples

彼の話は落ちが弱くて、あまり笑えませんでした。kare no hanashi wa o chi ga yowa ku te a ma ri wara e ma se n de shi ta

The punchline of his story was weak, so it did not make us laugh much.

Brings a story's buildup down to one decisive ending that produces the intended laugh.

サゲsage: A closing line or action that ends a comic story and produces its final laugh.

話の流れを最後に意外な一言や展開で締めくくる部分。hanashi no naga re o sai go ni i gai na hito koto ya ten kai de shi me ku ku ru bu bun

落ち (ochi) is the noun form of 落ちる (ochiru, "to fall"), and the word extends the idea of falling to the concluding point of a comic story.

Rakugo performances traditionally build toward an 落ち (ochi), making the closing line especially important to the comic effect.