A fork of Rural Dictionary
The part of the brain that holds the capacity for laughter, humor, jokes, etc. It's small, smaller than the medulla oblongata, but is somehow big enough to store decades of fart, sex, golf, and poop jokes. Without the Hahaguffawchuckleamalus, we'd all be as boring and humorless as a university professor, or the entire country of Russia.
As part of his plan for world domination, Professor Poopypants shrank the Hahaguffawchuckleamalus of the students of Jerome Horowitz Elementary, turning them into boring, mindless zombies. Luckily, Captain Underpants defeated him and saved the day.