A worst birthday is when a man ejaculates onto a woman as the stock market simultaneously crashes and the woman loses her house, causing the woman to exclaim "Whaaaat?"

It is considered rude.
Mark gave Sarah a worst birthday and everyone in town pretty much agrees now that Mark is a rude man.
by L. Baines. J. January 30, 2008
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a phrase to use when something goes completely wrong or life sucks. (Mark Baker 2007)
'waaaaa, i failed therms. worst birthday ever'
by lea-unitt. June 15, 2007
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