The ability to cause heads in the immediate vicinity to explode. This includes one's own head.
In Jhonen Vasquez's comic, Johnny the Homicidal Maniac, the main character 'Nny visits Heaven, having beeen denied entry into Hell. While in Heaven, 'Nny learns that, like all behind the pearly gates, the ability to explode people's heads has been conferred upon him. Very messy antics ensue, preceeded by an exclamation and a blood-thirsty grin, "I have Head Explody?!"
by Chris N. September 11, 2006
An intense headache.
I'm going to grab some tylenol and lay down till the headexplodies pass.
by Black August 19, 2003