尻しりすぼまり

na-adjective, noun which may take the genitive case particle 'no'

tapering off; fizzling out; dwindling

Describes something that starts strong but gradually loses momentum, intensity, or size, like a story, event, or trend that ends weakly.

• 彼かれのスピーチは尻しりすぼまりで、最さい後ごは何なにを言いっているのかわからなかった。

  His speech tapered off, and by the end I couldn't understand what he was saying.

• 景けい気き回かい復ふくは尻しりすぼまりに終おわった。

  The economic recovery fizzled out.