何なんだい

expression

what is it?; what's going on?; what is that?

Colloquial, often used by men or in casual speech. The だい ending adds a familiar, sometimes blunt or friendly, questioning tone.

• おい、何なんだい、その格かっ好こうは？

  Hey, what's with that outfit?

• 何なんだい、急きゅうに呼よび出だして。

  What is it, calling me out so suddenly?