Mardi Gras = also know as Pancake Day (and literally translated from French to "Fat Tuesday"). Traditionally this was the last day before Lent, so all the delicious, fatty food (butter, milk, and eggs for pancakes) was used up before fasting during Lent started.
These days, in Australia and New Zealand, Mardi Gras is synonymous with the Gay Pride Parade, a huge event held in Sydney every year. Many other cities hold similar festivals, celebrating diversity and acceptance of LGBTQI* rights.
Even with their British heritage, eating pancakes on Pancake Day (also known as "Shrove Tuesday") is traditionally not as big a celebration in Australia or NZ as it is in the UK.
Example: We are going to the mardi gras after party this weekend.
Pronunciation: mardee - grah
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*Lesbian, Gay, Bi-sexual, Transgender, Queer/Questioning, Intersex