ネタばらし

noun

spoiling; revealing a trick; giving it away

Refers to revealing a story's twist, a magic trick's secret, or the punchline of a joke. Often used in entertainment contexts.

• 映えい画がのネタばらしをしないでください。

  Please don't spoil the movie.

• 手て品じなのネタばらしはタブーだ。

  Revealing the secret of a magic trick is taboo.