noun, noun or participle which takes 'suru'
Children's language for putting things away or tidying up; often used as a playful command or when talking to small children.
おもちゃをないないしようね。
Let's put the toys away, okay?
ごはんの前におえかきをないないして。
Put away your drawing before dinner.
i-adjective
no way; no chance
Emphatic repetition of 無い; used as an interjection-like expression to strongly deny or reject something. Informal and colloquial.
See also: 無い
そんなこと、ないない！
No way that's true!
彼が遅刻するなんてないない。
There's no chance he'd be late.