Many different societies around the world have slang unique to that location but none seems more bizarre to people in other parts of the world than the slang that comes from Australia.
The average Aussie has slipped some sort of slang in their day to day only to travel to another part of the world and have the locals not understand what they are trying to say. Personally, I use the word "mate" more than any person should. Here are some examples of other Aussie slang that is incredibly common to Australians but makes no sense to our friends elsewhere in the world.
The summer we just had was awful.
Although everyone is "mate" to me.
Also... anyone keen for a Maccas run? hit me up. haha