You decide, and we'll just take your word for it.
Is it a really intense burp that only happens when you drink pop rocks and soda during a full moon after saying an evil incantation, and results in you "blurping" up a skull-demon? but we've still been too chicken to try it out for ourselves..Or, is it the sound you make when you sneeze really hard with your mouth open, and you yak up your own bones? What if it turned out to be true, though? Isn't there an old urban legend that says if you sneeze with your eyes open, your eyeballs will fly out of their sockets? It can't possibly be true, because heads don't work like Nerf guns.