Heavily used slang in Australia. Used when you are reluctant to commit to a firm answer. Yeah nah is another way of saying yeah I hear you but no is the likely answer. While nah yeah is like saying I don't agree with what you saying but yeah is the likely answer.
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
Yeah = yes a) I understand the question, b) it was me, c) i might agree with what you are saying. Nah = No a) I don't think thats right, b) it was not me, c) there is no useful information i can give you, d)come to think of it, maybe i don't agree with you. I dunno = I'd like to put in a disclaimer and nullify anything I just said. Non committal. Common in Australia.
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.