When one has to take a shit with great force. Causing your bathroom to smell horrible and sometimes causing explosion outlines inside your toilet bowl.
Oh man this burrito I just ate fucked up my stomach! Im gonna blow it up when I get to your house!
A celebratory gesture which builds upon the pound it, meant to replace the high five. To "blow it up" you simply pound fists and while retracting from the pound both parties open their fists quickly while making an exploding sound.