There isn't really a greeting that is particular to Australia. 'Merry Christmas' or 'Happy Christmas' would be the main ones.
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Please note there is no such language as "AUSTRALIAN", most people in Australia speak ENGLISH as their first language (with an Australian accent). Thus Australians would say "Merry Christmas".
I have mostly heard them say Happy Christmas!
Santa, Santa Claus or Father Christmas would be the most common forms of address for the old gentleman.
A peculiarly Australian title for him which I have not heard for many years and which may have originated from a funny story was, Whacker Chimber.
Some Australians call him Father Christmas.
Others call him Santa Claus.
Some call him "Santa Claus", same as in North America, some say the original "Father Christmas", as they do in Britain (Australia was settled by the British).
There is no such language as "Australian". The official language of Australia is English so you would say "Merry Christmas".
Santa, Santa Claus, Father Christmas.
Merry christmas
Santa Clause
"Merry Christmas, mate!" English is the predominant language in Australia, so you say it in exactly the same way except with the addition of an Australian accent. Or: Usually you just say "Merry Christmas" or "Happy Christmas". In the vernacular, you might say, " 'Ave a good one, mate."
Just as in your question !They tend to say "Happy Christmas" instead of "Merry".Merry Christmas
You say ' Merry Christmas' in the UK.
merry christmas
merry christmas
"Merry Christmas"
Merry Christmas
Merry christmas
merry Christmas= Christmas aashamsakal
Hanukkah is a holiday, not a language. You cannot say "Merry Christmas in Hanukkah. That's like asking: "How do you say Merry Christmas in Easter" I think he means how do you say merry Christmas in Hebrew
Merry Christmas
Merry Christmas