To behave with the extravagance, decadence, or moral depravity associated with the Roman Emperor Heliogabalus.
From Heliogabalus, a 3rd-century Roman Emperor famous for his luxurious and controversial lifestyle, plus suffix '-ize' (to make or cause).
Heliogabalus is basically the historical byword for wild excess—the emperor was so famously outrageous that his name became a verb to describe over-the-top decadent behavior!
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