Generally means that you understand a statement or that you agree with a statement. Typically is followed up with an explanation of how or why you agree with the previous statement made by the other in conversation.
"Are you aware that if you do not wear a condom, you may end up with a sexually transmitted disease?"
"Nah-yeah, I have several STDs as a result of not wearing a condom."
Australian slang, doesn't really mean yes or no just used in conversation when you're trying to agree with someone i have no fucking idea im australian and idek
-The Mike Nolan Show
"What do you do Nollsy?"
"Oh yeah nah nah yeah just a bit of that all"
An extended Australian term of "yeah no", this comes from down under, where the Aussie blokes speak gibberish, because of their short vocabulary. This term only comes Australia, as kids gotta be 'true blue australians' to comprehend its true meaning. If you hear someone say this, you betta run and hide, because these kids play rough.
"yeah nah yeah nah, can't go down to da quicky mart, nahhh."