The act of eating so much confetti (or candy) till you're shitting nothing but in, then hanging yourself naked with a grenade in your anal cavity with a note tied to the pin saying "haha enjoy" and waiting for someone to find your body.
Person 1: Dude you look sad, what's up?
Person 2: My dad human pinata'd himself last night and I fell for the note.
A human pinata is like a regular pinata except instead of bashing a nonliving pinata with a stick, you bash a human with a stick over and over again. Just like when candy pops out, you succeed by making guts and blood pop out. If the human dies, you know you did it correctly.