A general insult. Normally used when some one does something that really ticks you off. Although some people use it for no aperant reason.
What the fuck was that ass jackolantern thinking when he pulled in front of me?
Masturbating using a Jack-o-lantern
Person 1: What did you do this Halloween?
Person 2: Just Jackolantern inside my room
When a pumpkin hits something hard
He wasnt a normal pumpkin hes a jackolantern