The merlion is a hybrid between a lion and a fish. In Singapore, there is a merlion statue / fountain which expels water from its mouth into the sea. It is a national attraction and an icon that attracts lots of tourists everyday.

'to do the merlion' is a term to describe people who vomits non-stop in a violent nature - similar to what the merlion which 'pukes' out tons of water every second.

Usually meant to describe people who pukes for long duration after excessive drinking or encountering something extremely offensive.
After the dinner and all that alcohol, John did the merlion in the toilet the entire night

Realizing he had actually swallowed his best friend's semem in a stupid prank he did the merlion
by tengatango sextoys December 18, 2010
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