Telling a joke that is incredibly unfunny, but insisting on repeating it to everyone you know.
Can also refer to a prank or joke that was pulled, but isn't funny, yet the original prankster insists on telling it over and over again to everyone he/she knows.
Hubert: Why did the chicken cross the road?
Chris: *sigh* ....why?
Hubert: To get to the other side!! LOL HAHAH
Chris: ....that's just A-Paul-ing...