Robespierre was an important figure during the French Revolution and when the consul decided to put him to the guillotine he tried to commit suicide.
Instead of shooting himself through the jaw he shot off his jaw and was unsuccessful in killing himself, but he was still put to the guillotine.
To pull a Robespierre is the act of successfully trying to kill oneself esp. attempted shootings through the skull (by holding a gun under ones jaw), but turning out unsuccessful and shooting off ones jaw
how to pull a Robespierre:
Get a gun
put it to your jaw like a gangsta (making sure the gun will only shoot off your jaw)
* Now you have successfully pulled a Robespierre
Situation: Jim is in the hospital for attempted suicide
Bill to Mike: "Dude, what happened"
Mike to Bill: "Nothing, but Jim pulled a Robespierre. I heard he did it for the lulz"