Nah

[Britney]

No. Nah and no mean the same thing. Nah is often followed by man. As in nah, man.

[Becky]

Da Gangsta way to say No

[Sarah]

An expression used when the aforementioned statement sounds incredibly unfeasible/stupid on closer hearing.

[Mark Zuckerberg]

nah a typically turkish cultural gesture which expresses misbelieve, distrust, challenge, opposition or disobedience. nah occurs when someone puts his/her thumb between forefinger and middle finger and the nahhed fist is shown to the person at whom it is aimed.
a more brutal version of the gesture exists, by creating a slash like sound after turning the nahhed fist with an immediate forward motion, in order that the nahhed wrist hits the other hands palm.
literally nah means like the hell it is?

[Jessica]

This is the shortage of na huj (на ХУЙ) - nah, wich means fuck no or I dont care. Most popular slang word in russian language between young ppl for long time (ages).

[PussyCat]

Nah: (Nn-ahh) Noun. A word commonly used as a replacement for no, nope, shut up, or no, dont give me that food, I dont want to get fat. But mostly no.

[Dave Paprocki]

A guy who you like the thought of and seems pleasant but has a horrible horrible personality.

[Zipporah Schumaker]

Nah stands for no as hell

[Justin Bieber]

Nah alternative way to say no.

[Dave Paprocki]

Used when no is too formal, and nope is too casual.

If its ever capitilized, youre using it wrong.