Commonly used with males in the ages of 10-20. These males exhibit a need to be cool with the crowd. This can often work if the objected audience answers "yes".
However, caution should be used to avoid using the term "nah mean" when the answer will be "no". This can result in a loss of coolness, thus, defeating the purpose of the term "Nah mean".
Some have also given responses with N' mean. Shortened for the phrase "I know what you mean".
Andrew: N' mean.
Martin: I think all blondes are dumb. Nah mean?
Andrew: Nope...I think you're dumb.