An orgy, traditionally occurring on the the 25th birthday.

A birthday party in which all of the birthday person's favorite people are invited to have sex, although not necessarily with the birthday person.

A right of passage, every person is allowed at least one Orgy Birthday.
"It's Sarah's Orgy Birthday this Saturday, what should I get her?"

"Bring a partner and condoms!"
by Patina December 1, 2009
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