to do something so dangerously stupid in public where one causes harm to oneself.
That kid riding his skateboard on the guard rails fell on his head. He really plaxicated himself in front of all those onlookers.
To embarrassingly harm oneself by executing poor judgment.
Person A: "I was supposed to give a presentation this morning in front of the board members, but I set my alarm for PM instead of AM."
Person B: "You went and plaxicated yourself, son!"