interjection
what?; what'd you say?
Colloquial, jocular corruption of なに, used to express surprise or to ask someone to repeat what they said. Often used playfully among friends.
See also: 何
なぬ？ もう一度言ってくれ。
What? Say that again.
なぬ、そんなことがあったのか。
What, did that really happen?