The fart bubble that is stuck between your ass cheeks that won't come out no matter how much you squeeze your cheeks.
Whats wrong with you Tim?
I got a corked fart and it won't come out!
Noun: The last fart you have before pooping is imminent. Sometimes you don't even realize you need to poop until the cork fart is released.
Alex: *fart noise* Oh boy! I need to get to the bathroom!
Erin: Was that a cork fart?
Alex: Yup, got to go!
Erin: See you in a half hour