An event involving completely shaving one's head, be it to support a cure for cancer or just for the lulz. It takes place around the time of Saint Pat's day.

Can also be used as a verb.
I plan to shave my head for Saint Baldrick's Day.

or

Johnny: Dude, I just Saint Baldricks'd!

Gaby: I'm gonna miss your epic hair...
by ChingChongPotato March 12, 2010
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