Nah kid
The words you say when you're pretending to be cool but you're actually just avoiding something. It's like you're being a snob but you're not even trying.
Nah kid, I'm not coming to your concert. I don't like your music.
Nah kid, I'm not eating that. It looks like death.
Nah kid, I'm not doing that. I'm too cool for your level of nonsense.